There is a club in Edinburgh (listed on this site), it uses inverleith pond. I would suggest you contact them, find out when they meet, find out who sails the type of model you want and have a talk.

Hi
Welcome to the site.
I suggest you buy a copy of the Model Boats Magazine to see what might appeal. You can then contact one of the advertisers to get more details.
If you need a ready built model you can usually find one on e-bay or in a local auction. There are pitfalls and if you can find a local friendly Model Shop or Club they will guide you in the right direction.
Good hunting