Hi Marc,
Its a slippery slope once you've started buying things.
The default online shop is
http://www.chainreactioncycles.com/ as you can get near enough everything.
I look at all sites and worth keeping an eye on the Vouchers/offers/deals thread on here for the latest deals etc.
Once you start "needing" to bling, people like
http://www.superstarcomponents.com/ can come in handy.
Other bargain places to keep an eye on
http://www.merlincycles.com/http://www.on-one.co.uk/oh the list is endless.
Check the ride calender at the top right for any local rides.
Welcome along.