Apple Store
Although not in Chapelfield, Norwich does have an official Apple Store located inside PC World on Sweet Briar Retail Park. It is done to look like an Apple Shop. It is one of Apple 'Shop-in-Shop' projects. It has an official Apple Solutions Consultant on hand 5 out of 7 days (generally off Tues / Weds).
They have stock all the time and can do certain upgrades. Not just CPU but also many accessories and various software. They also sell AppleCare, which no retailer sells on the high street.
Jon, who is the Apple Professional on hand, is very knowledgeable, and vert helpful.
I suggest that any Apple needs you have, you should see him.