There are plenty of very good British films. To be honest, it's very often down to the distributors not believing that an American audience will get into some of them so don't release them there. But there are plenty of very properly British films that don't pander to any international audiences - e.g. Trainspotting, Hot Fuzz, Secrets and Lies etc. And if you find a British film with an American actor in it then you know they're pandering to a US audience.