That is excessive. by some margin.
sadly all dealers will sting you for tyres. Assuming these are pirrelli or bridgestone i can see then charging £150+ for one of these fitted. (you can get 18" eagle F1s fitted for £95 if you
shop around. camskill.co.uk for example) 17" probably £80.
But that still leaves £310+ for the service which is expensive by a big margin.
Have you got a breakdown of what they did costs etc. Did you give go ahead for tyre? did they give you a price for the service and tyre before doing the work?
byt he way there is another thread going at the mo about servicing, some interesting comparisons regarding costs there:
http://www.seatcupra.net/forums/showthread.php?t=150031