I would say that RP is the accent associated with Oxbridge and the major public schools. The BBC accent is not RP, indeed Ed Stourton (Posh Ed) has suffered as a result and the former India correspondent (whose name escapes me) lost his job because of it.
It's probably just the meaning of the labels that divides us on this. URP I haven't heard of.
I think that cockney and upper-class English were broadly similar at one time. The newly-emerging middle classes were the engines of change, with their tendency to alter pronunciations to conform with their spellings - the speak-as-you-spell phenomenon against which Fowler inveighed so much.

It's 'Received Pronunciation' - what in Britain is perceived as an 'educated' accent.

Agreed. I'm English and I've never cared for the 'paw' rendering for 'poor'. 'Tour' can't possibly be 'taw' but many English people do say it that way.

Americans, I notice, drop the 'l' in solder. It comes out as 'soda'. This is old-fashioned English. The 'l' in 'soldier' was also dropped at one time. That's why Kipling, in his phonetic rendering of cockney speech, uses the word 'sojer'.

Yes, "an 'otel" was correct Englisn until not so long ago. My 99-year-old mother-in-law still says it that way. "An hotel" is an absurdity.
Good for the Americans with their " 'erb"!
Cockneys are great preservers of old-fashioned pronunciation. The cockneys still say "gorn orf" for "gone off", as did the upper classes until recently. And also "awspital" for "hospital". Good old-time English.
In the nursery rhyme 'Ride a cock horse to Banbury Cross' the word 'cross' has to be pronouced 'crawse' in order to rhyme - the cockney way.

'Passers-by' and yet 'passer-by's'. I got an ignorant red squiggle because of that closing inverted comma!

Other possibilities, I see belatedly, are 'petits cotes' (with accent) and 'petites gastelles'.

In fact, the contribution of French to Scottish English would make an interesting thread in its own right. There is 'petticoat tails' from 'petits gateaux', for example and 'fash' - as in 'dinna fash yesel - from the French 'facher'. Yes, I know there's a circumflex...

'Brings in', blast it.

'Text' is 'written', surely?
'I wrote you a text.'
Back in the real world, though - yes, it's 'texted'. New technology - like the printing press in days of yore - always bring in new words.