Ouch! £17 every three months would get pricey, but it sounds like you've gotten a good one now.
I'm with Judes on this - I paid the same amount for my North Face. Sylar earlier said it was too expensive for a rucksack, but IMO it depends on what utility you get from it, and how long it lasts. My plan is that if I get say three years out of it, I will have paid £3.60 per month. I use it every day.
@Judes, yes, a pocket at the front is very handy. Train pass, small bike lights, money, etc. without having to dig into the bag recesses too much!