No doubt it isn't as good as in America but there is one of these in Northampton and one in Milton Keynes now too:
http://www.rodizios.co.uk/index.html
I went to the one in MK a few weeks back and it was ok, meat was very good when it came but that kind of service means you can be waiting a while for the bbq to come round.
As for TGIF, I agree that it is kind of overpriced for what it is but I have found the quality of the food to be better than you'd get in the other average chain places (Frankie & Bennies, Nandos, Pizza Hut that were mentioned). The atmosphere is usually good but it depends a lot on the staff, went to one in America that was dire. Haven't been to one for a while though.