Whilst looking back the comedy hasn't aged well and is certainly in some places, very cheap..
I don't think it was racist, of course my opinion as a white person there counts for very little..
They didn't use white actors to play black characters on purpose, they played ALL the characters themselves, black, white, female, male...
I don't think it was offensive from a disabled persons POV either, and my opinion there does count - I do a mean Andy impression whenever I think someone is staring at me and particularly if someones pushing me... it makes people think twice!
Little Britain played on stereotypes and tried to take the piss out of all of them, and it did that, and it made us look at stereotypes and realise how ridiculous some of them are.
Are we now to deny that stereotypes exist, and exist for a reason, because humans do need to categorise people and will always do so, and because there is some truth to every stereotype somewhere?
Stereotypes are not a bad thing - refusing to realise we've stereotyped someone wrongly, judging and basing decisions on that snap judgement when faced with evidence to the contrary.. those things are whats bad.
As far as Lou and Andy goes, Andy sat in a wheelchair and Lou assumed he was disabled, as far as I know, Andy never actually said he was - the joke for me is not Andy, it's Lou who made assumptions and has never actually questioned them.