If you don’t have a gift for mimicry you aren’t going to be able to fake an accent no matter how long you’ve lived around it. I speak from experience here.
In my lifetime I’ve only heard cheerio said occasionally by Scots, but that includes very recent examples, so I’d say it’s genuine but not south of the border.
Pip-pip has probably never existed outside the world of P. G. Wodehouse and similar authors writing parodies of the aristocracy/upper middle class. Tally-ho is supposed to be a cry used by people hunting foxes on horseback (which are about as common where I am as rodeo riders are in New England). Even that may be obsolete AFAIK. People might use either expression for comic effect, but not for everyday purposes.
If you are from the west coast, you have a “surfer accent” to everyone else. There is a sound to the west coast accent that is in kin with surfer. 
I didn’t notice it at first (being from the west coast myself) until I moved out of the urban areas and lived on the Oregon coast for a few years -where people mostly speak with a lazy half county twang.
All my old friends from Washington who used to sound normal sounded more like Jeff Spicoli (Hey bud,. heh heh, let’s party)
The other day I heard a snippet on Radio 4 from a play currently on at the Edinburgh Festival on the life of Saul Bellow. Judging from the excerpt I heard, the actor playing Bellow apparently studied at the Monty Python School of American Accents. Dreadful.
You obviously were never in a pub in England anytime Germany were knocked out of a major football competition.
I’m no expert on this, but Belle and Sebastian used the term “cheerio” on their song Le Pastie De La Bourgeoisie.
“cheerio” was coommonn enough when I was young, but seems to have gone out now. I being Scottish, that might prove the point made by other posters.
Oh, and it meant “goodbye” NOT some bizarre breakfast cereal!
eeek - meant “common” - bad old eyesight typing into the sun here. Oops. 
I’m sure postman Pat used to say it!
Hell, in The Musketeer, the moppet they had playing D’Artagnan couldn’t even pronounce D’Artagnan! He kept sayin “Dartin”.
Well I certainly have been (surprise surprise), but c’mon, chant lyrics don’t count. You wouldn’t expect to hear it in everyday conversation down here.
Probably true. Animated postal workers whose best friends are cats don’t count either. What decade is it in Greendale anyhow?
http://www.letssingit.com/belle-and-sebastian-le-pastie-de-la-bourgeoisie-f1j9cm5.html"]Correct. Scottish band of course.
I’ve got one mate who says it all the time. He’s in his early thirties so It’ll be amusing to gauge his response when I tell him how out of date he is ;).
As a 29 year old Warwickshire boy who uses “Cheerio”, I am somewhat confused by the direction this thread has taken.
I too use the “cheerio” word occasionally. I’m 35.
I use “Cheerio” too, but only to refer to a single piece of a particular type of breakfast food, as in, “Oops, I dropped a Cheerio; careful where you step.”