Genuine RS500 Cosworths are now pretty rare. A lot of them were used as race cars so met untimely deaths that way. The remaining road going cars nowadays have mostly been modded or thrashed to within an inch of their lives so you would be brave to take one on. The are a few good examples around tho. I'm no expert on them so could not quote prices to you without checking but a clean original example would cost a lot so I think you would REALLY want one to shell out that much cash.
The more common saloon bodied "Sapphire" Cossies are a lot more common and you can sometimes see a couple a day on the roads. They are now a real bargain if you can find a good one, which would be a task in itself. Most have been crashed, thrashed and generally abused and due to the general "average" build quality and the fact they ceased production around 1992-93, most are in a pretty poor state. They were one of THE cars to have in the late 80's and as a consequence quickly became the thief and "joyriders" car of choice. This of course sent insurance premiums through the roof so few could afford to drive them(legally
). This drove prices down and nowadays you would probably get a half decent one for £5000? I'm not really sure about exact prices as I have never really been into Fords in a big way.
Escort Cossies are quite common and still fetch good money. You see a handful in most of the larger car mart mags but it's finding the ones that aren't gonna empty you bank balance that is the problem!! I've never been in one but I'm told they are awesome to drive and can put out silly power if you spend money on the right things!!
I'll have a trawl and see if I can find some of the UK RS and Cosworth forums if you want?
With regards to the Integrale, they are pretty rare and good ones are even harder to find as they were import only vehicles. I have a mate who bought an absolutely mint EVO1 recently from a guy who imports cars direct from Italy. The car is a 1992 "Monte Carlo" special edition with about 45k on the clock and it is stunning. It cost him around £9k tho which is really the going rate for a nice example. These cars are in a similar supply to the Cossies, many have been abused and you have to look really hard to find a good one. It is a mean car tho and goes like a cat with it's ass on fire!! I'd have one over a Cossie any day!!!!
Have a look here:
www.exchangeandmart.co.uk
This is one of the largest UK used car advertisers.