Problems getting credit but WHY?!!!?

I've got a really good credit history, I have checked my credit report and it is all good, no missed payments or CCJ's etc on the electoral role at my current address, I even checked my credit score and it came out as 999 out of 1000 but yet when I applied for a tesco credit card they said no because my score wasn't high enough! I haven't been able to get credit now or even a bank account for about 2 years! I don't get it! (I haven't applied for many so there aren't loads of searchs on my account either) How can I find out EXACTLY what the problem is as all experian tell me is 'your report looks fine' I have ordered my equifax report but can't see it being much different, do many lenders use call credit? is it worth me checking that one too? HELP!!!!