Prestwick
I recently diverted to Prestwick on my way to Inverness and they couldnt have been more helpful. Cost was quite a bit higher than where I normally go but they did look after my plane for three days and sort a hire car. Fuel was ridiculously priced!
I wouldnt worry about them accomodating GA traffic as there was loads around there.
I also spoke to Oban who were very helpful but I never got there. I am going to go there some time soon to meet my friend with his boat which lives somewhere near there.