All of the UK.
Silly me, when you said “outlets in bathrooms are illegal” I thought you meant “outlets in bathrooms are illegal”.
That’s no different than in the US, when all outlets near plumbing are required to have a GFCI circuit breaker in them.
The difference us that American women can dry their hair and use a vacuum cleaner in the bathroom. 
Yes, they prevent it from working with vacuum cleaners and hair dryers using the complicated technical solution of printing “shavers only” on the outside of the outlet.
Damned clever of them, too.
And by having the design of the socket totally different from a normal electrical outlet. In the UK it is only shaver sockets that have that two-pin design. Normal household sockets look like this.
Hair dryers and vacuum cleaners have three-pin plugs. I suppose you could get round it with some kind of adapter but I’ve never been tempted. In fact that probably would be a bad idea, quite apart from the water issue, because AFAIK the shaver sockets are often (usually?) run off the lighting circuit and are only designed for low currents. Trying to run a powerful hair dryer off it would fry the wiring.
The charger for my electric toothbrush, however, has a shaver-style two-pin plug, so I plug it into my “Shavers Only” socket with impunity.
And by having the fitting being completely different, so there’s no way (without rewiring) to connect your hairdryer or vacuum cleaner to a shaver point.
The lower ceiling is almost always to permit piping and ducting without encroaching on valuable floor space, whether it’s within rooms or within common areas. It isn’t done in houses because few houses have such constricted floor-to-ceiling limits (between structural floors in a large building) and the attic and basement or crawl space is available for such things.
I grew up in a late-1950s house that had a dropped ceiling in the hallway to accommodate the HVAC ducting without excessive side runs - there was one decreasing-diameter feed all the way down and short side runs to outflows over each bedroom door. My last house in California was of similar vintage and had the same dropped ceiling, which I came close to raising twice except that it gave the passage a sort of groovy spaceship feel. 
It wasn’t actually me who said the outlets were “illegal” - it’s not like it’s a criminal offence to put an outlet in the bathroom. Probably the best way to think of it in US term is as a code violation.
But they are different - there is, as I pointed out, an isolating transformer to reduce the shock risk.
Anyway, addressing the original question:
But in a home you usually have a roof void above the bathroom to cope with ventilation etc. In a hotel the space above the bathroom is usually… another bathroom, so you need a hidden ceiling to conceal all that stuff.
Might I add a few additional questions about hotel bathrooms? One about hotel bathrooms in the US; one about hotel bathrooms in Europe.
In the US, I’ve noticed lately that they’re not terribly fond of shower curtain liners. Is this just because they tend to build up soap scum and other nastiness? One would think they could get some sort of very cheap disposable liner that they change between guests. I’m a bit tired of irrigating my hotel bathroom floor when I take a shower.
In Europe, they’ve got a different approach to making sure that most of the water winds up outside of the shower: rather than any sort of shower curtain at all, they’ve got a little glass partition-door thing that covers, at max, half of the bath enclosure. The shower is usually of the handle on a hose type. And there’s nothing to actually secure the little glass enclosure door, so if you nudge it, it swings. And like I said, half the bathtub tops. 1/3 is probably more like it. This one I don’t understand at all, and can’t even speculate on.
Probably through the circuit breaker.
Do they have circuit breakers in the UK?
Transistors are called “electronic valves” in the UK, which is much more descriptive of their function than “transistor”.
Yes, we have circuit breakers or (in much older installations) wire fuses. Typically, overhead lights are run on a circuit fused to 5 amps. Outlets are run on a ring circuit fused to 30 amps.
Shaver points are normally connected to the 5 amp lighting circuit and yes, this is determined by the circuit breaker at the main panel.
I’m no EE, but it seems that would be a better description of a diode.
[quote=“Gary “Wombat” Robson, post:15, topic:668653”]
At 6’5", I’m tall but not freakishly tall like a basketball player. I’ve stayed in several hotels/motels (and a LOT of motor homes) where I couldn’t even stand up straight in the shower because the ceiling in there was so low. I’ve resigned myself to getting down on my knees to shampoo my hair in many hotels.
[/QUOTE]
I’m 6’3" and I have never been able to take a proper shower … until last summer.
We had our bathroom gutted and rebuilt. The contractor was a friend, so he gave lots of good tips and was looking out for me as he did the work. He had me stand in the shower and he put the showerhead at the absolutely perfect height.
Now I can shower while standing straight and tall. Even a year later I still feel joy as I step into my custom shower. The glass guys were good to me too; they put in sliders that are are several inches taller than the normal height.
All you tall folks out there: if you are ever renovating a bathroom, get it done custom for your height.
A diode would be analogous to a check valve that only lets a liquid flow in one direction. A transistor controls the amount of current that flows through it.
Nah, a diode would be more analogous to a backflow preventer. Valve has the connotation of controlling flow, usually with an adjustable volume – pretty much what a transistor does.
I thought that was what a check valve is. 
Oops, NM
If there is only a curtain and no liner, then the curtain goes inside the tub when you shower and water doesn’t or shouldn’t hit the floor. The reason not to have a liner, apart from cost, is that moisture tends to be trapped between the curtain and the liner, and this encourages the growth of mildew or mold.
In Massachusetts the switch for a bathroom light must be outside the bathroom by code, or at least this used to be true 30 years ago.
Now we have Americans peeing on their shoes!
You would think a DC low voltage relay would be used.