I guess for a boat modeller, places like the model dockyard take some beating. Ship and boat modelling has a much smaller userbase than cars and aircraft, so you can't blame model shops setting their sights on those markets.
All the same, I always think it's good pr for amodel shop to take the time to order in a part or two, especially if you're a regular customer. One shop that always gets the thumbs up from me is 308 hobbies in Holloway Rd (used to Henry J Nicholls years ago).
Although like most model shops, they are geared towards the car and aircraft market, they carry quite a few boat bits, and are happy to order in bits and bobs so long as they are catalogued.