I've had curry in many Australian cities, and a few UK places. They're different, and what you prefer would likely depend on where you're from and what you're used to. I like both styles, and have had good and bad meals in both countries. Sydney for example, has never won me over with their curry, yet I've had great curry in both Melbourne and Brisbane. Gaylord in Soho (London) was great, as was one of the places I went to in Leeds. Brick lane however, has held mixed results for me, with 2 good meals and 1 bad so far. Chutney Mary's in Chelsea was a highlight, as was a place in West Drayton, near Heathrow airport. The main difference can be found right here on this site, in the different base sauces. BIR curries use a soupy base and the final dishes tend more towards a sweeter, less spicy flavour. AIR curries use a concentrated base mix with more spices and onions, and the final dishes reflect that. As I've said elsewhere on this forum, the Vindaloo is a perfect example of the differences between the two. BIR Vindaloo is a hotter version of a Madras, and may only have a small amount of vinegar for the tartness. AIR Vindaloo is very tangy, and as Masala Mark has noted, AIR's use a concentrated base plus Vindaloo paste to give it that flavour.
Both different, and if cooked well, both great IMHO..