providing you get a decent loan you should be able to pay it - 100pw for 42 weeks is a pretty normal contract which is only £4200 a year, half your student finance if you get the maximum (and if you get the maximum you'll also get a bursary from your uni)
there are cheaper and more expensive places though, I paid between £55 and £70 pw during uni and, as others have said, in some places £100-150 is normal