Marina websites often given good navigational information concerning their relevant port/harbour.
Brighton Marina
Southsea Marina, Langstone
Langstone Harbour
Chichester Harbour
Haslar Marina, Gosport
Gosport Marina
Royal Clarence Marina, Gosport
QHM Gosport
River Hamble Harbour Authority
Cowes- navigation info
Cowes Yacht Haven
East Cowes Marina
Lymington Yacht Haven
Yarmouth Harbour
MDL marinas -
The MDL site covers:
Queen Anne's Battery (Plymouth), Brixham Marina, Torquay Marina; Cobb's Quay (Poole), Hythe Marina Village, Ocean Marina Village , Shamrock Quay (Southampton); Hamble Point, Port Hamble, Mercury Yacht Harbour, Northney Marina (Chichester); Bray Marina, Windsor Marina, Ponton Hook Marina (all on the Thames); Chatham Maritime Marina, Woolverstone Marina.
Guernsey Harbour Authority - navigational and other info
St Helier
Cherbourg