Andrew,
have you checked your credit report ? sometimes there are things on it that you dont know about. its worth having a look for piece of mind.
another thing is that you dont seem to have a credit trail... ironically, if you dont have any credit facilities that normally goes against you as well. my parents wanted to purchase a new bed and , although they could afford the whole amount, they wanted to take advantage of the interest free period ... guess what they - got declined because they had now credit history.
you need to get something that shows a track record.
hope this helps, get your credit rating first.
George