We must be rather spoilt here where I live, when I read the problems you seem to be having in the UK. We had a dedicated model shop in Ballina NSW Australia, where our marine modelling club is located, but it closed, and the owner, who is a member of both the marine modellers and the model flying club, kept his business accreditation, and now operates from home, while both he and his wife work in other jobs. The down side is that there is no shop front for us to go to, but the up side is that all are welcome at his home at most (reasonable) times, just ring first to ensure he is home, and he carries a good stock of most items applicable to both hobbies. We also have a big hobby and toy shop in Lismore, about 40km (25 miles) away, also run by a modeller, which carries an extensive stock of modelling gear, and the cheapest prices on Futaba radios I have seen anywhere. Mail order within Australia is also an option, with quite large hobby shops operating in Brisbane, Newcastle, Sydney, and Melbourne, with the Melbourne one being specifically for boat modellers. I have dealt with them all at various times, and have never had a problem with service. And of course, if all else fails, there is always the internet. I have found Westbourne Models to be particularly good, with excellent and speedy service, even to the other side of the world. In future, if I do have a supply problem, I won't feel so hard done by!
Peter.