I agree with you on all those points, except perhaps the notion that British films are just as far removed as Donnie Darko...
What makes British films so great these days is our directors' ability to highlight the key elements of what make us British and bring those true concepts to life. Although the films' might not portray ALL of Britain they often depict a scarily big part. Films such as Kidulthood and Bullet Boy for instance are underestimatedly brilliant but also very true to life for many British people.
As regards to the studios, yes!! We have no money in the UK to take chances but this is basically the point in hand.
Both of the two films mentioned above were made be small independent film companies raising funds off of their own back. The film council stopped giving money out years ago and lottery money is only available to non-profit organisations. Residue was funded mostly by the lottery it says from their website. Ex Cathedra, from what I can gather seems to have been made by York University graduates who raised the money themselves and worked for free to make a point. To show the British film industry that you can make risky films without having to risk a lot of money.
Regards to Brick, I think the cinematography of that film is superb and also definitely adds to the noir styling... however if you take the dialogue, soundtrack and cinematography out of any film your just going to be left with unprocessed film negatives