We bought our boat in the Hamble - not cheap, but there's every kind of service you would need. Plenty of marine engineers / electricians / sailmakers etc etc.
Finding a berth can be tricky, and the prices in the marinas will make your eyes water!
Some marinas have summer spaces when the berth-holders are out cruising. You won't get a price break, though. Services - yes, plenty, and probably competitive. Good showers at Moody's - complete bathrooms provided, also near train station and buses.