That's very strange!
Esp. considering students (mind you, these are guys just out of sixth-form/college who either work at McD's or don't work at all) get approved for £1250+ instantly, with only £2k or so (most of which goes on rent) coming in 3 times a year. They have guarantee a student will work during studying?!
I have been using my student credit card with Natwest (after finishing being a student) simply because if you then apply for a new one, they are more likely to decline you, because you have one already. The limit is way too low, and my subscriptions to various things always knock me over the limit, and I make a payment straight away, but they still charge me £12. This is hammering my credit rating, so I told them to shove it.