There seems to be a running joke that implies things “Made in Britain” are of inferior quality and prone to breakage at inopportune moments. I’ve seen it in many movies and TV shows, most recently during an episode of The IT Crowd (thank God for Netflix!) in which a British-made fire extinguisher actually bursts into flame. Can one of you self-deprecating Brits give me some insight into the history of this sentiment? As an American this doesn’t really jibe with how I perceive British goods - granted Rolls-Royce, Hobnobs and English ales are the first British goods I could think of, so perhaps my perception is skewed…
Not the best example this week. 
Automobiles, especially, used to have a reputation for poor build quality. The publicly-owned car makers, British Leyland, was a great national joke by the 1970s, though there was plenty of blame to spread around Ford (UK), Chrysler (who pulled out of Britain in 1979), and Vauxhall/GM too.
I think it’s a legacy from the 1970s. There was a “Buy British” government campaign at that time. But British manufacturing was then on its last legs.
For illustration, I refer you to the Bush brand of electronics, now a subsidiary of “Alba”, which are always the cheapest, have the worst sound/picture/whatever you need it to do, and fall apart within minutes of purchase. And cars made by British Leyland in the 1970s. Or, indeed, the Hillman Imp, our answer to the Trabant.
The quality brands you mention are indeed great, but they survived purely from the luxury market - regular people never got anywhere near them - and are now often owned by foreign companies.
I owned a Ford Cortina in the 1960’s and the people who say the Lucas three pole switch positions are “dim, flicker, and off” are correct. The worst electric system on any motor vehicle ever.
Why do British like warm beer?
Lucas makes their refrigerators.
That’s because it’s proper beer, not that freezing cold weasel’s piss that you lot call beer 
A couple of years ago when Rover was in its death throes, I remember a dude about to join the dole queue on TV asking somewhat rhetorically why “The French buy French cars, the Italians but Italian cars, the Germans buy German cars, why don’t the British buy British cars?”
All I could think was ‘Because we know who built the damn thing!’
As Mk VII alluded to, I think this idea gained ground in the 1970s. That decade was not a good time for British industry, with widespread strikes, general unrest and the three-day week. The general perception was that British-made goods were shoddy and overpriced, and if you wanted something cheap, whizzy and likely to last longer than your current diary, you should buy Japanese.
Old (probably apocryphal) tale:
On a condom machine in a men’s restroom somewhere in England were words to the effect of: “Old Blimey’s Condoms: Made to Exacting British Standards of Quality.” Scribbled underneath in pen were the words “so was the Titanic!”
Supposedly Lucas once made a vacuum cleaner. It was the only thing they ever made that didn’t suck.
Part of the joke/meme is that such products are typically emblazoned with a prominent ‘Made in Britain’ slogan, along with the Union Flag. The main reason for doing this is to get people to buy them out of patriotism (i.e. they do not stand on their own merits)
Back in the late 1970s or early 1980s, I saw a Jaguar with a bumper sticker that read, “The parts falling off this automobile are of the finest English craftsmanship.”
Making fun of “inferior British products” is a running gag in The Beatles film Help! (1965). Going from memory here, but the British scientist has more than one device, including a gun that falls apart IIRC, fail on him, and he makes a snarky remark. “British product, what do you expect,” or the like.
Yeah, at one point he laments “If I had a Luger…”
Don’t know how it started, but in the 60’s and 70’s in the US everybody wanted a British sports car for the looks, still knowing it would require an endless amount of repairs. I didn’t realize the Brits felt the same way about their products until later. It all seems to tie into the European national stereotypes, the English are proper but hapless, the Germans are rude but make things well, etc…
Anybody know what they think about American products?
Do we still make products?
That they’re all made in China.
ETA: jinx!
I remember reading one of P. J. O’Rourke’s humorous essays where he mentioned a Jaguar whose car alarm would go off randomly in the middle of the night, “in order to remind everyone where it had been built”.