I must recommend you get a haynes and do it yourself, shouldn't take a garage 2-3 hours either in my opinion, would take me 30-40 mins tops. It really isn't that hard a job, and will save you £100 nearly
I just had this done and they charged me £100 but this was in birmingham area! Along with a discount for always using this garage.
So no it don't sound a bad price, but shop around try a few garages.