Of course it's a high APR%. It's a credit card designed to help people with credit problems get a start on the ladder.
Which is why the limit on the card is £250. As with all credit cards, you should spend sensibly and pay off the card in full every month, and you won't have any problems.
This was the first credit card I ever had out of university as I had such a bad credit rating. A while on and it's still in use - I spend ~£5/month on it and pay the balance off in full every month, to carry on boosting my credit rating. It's helped me, along with other things of course, get to the point where I've now got a good platinum card with cash back (and sadly get loads of offers through the post).
Paying off your card in full doesn't do as much good for your credit history as keeping a balance on the card, as you're only using the card like it's a debit card.
Keep the balance at £5 and paying off anything over that would be a better approach if you're purely after building your credit history, but it will cost you slightly more.