If you need something fast, easy and inexpensive go for a 'castle playset' from the toy store. Faster and easier than building from scratch, cheaper than GW or most other castle models. But not as good looking as the other options.
- Ziterdes Castle Wolvenstein and Dwarf fortress - look lovely, how hard-wearing is the foam? Has anyone tried to convert foam buildings - easy or hard?
I worked with the NOCH foam models (wich is the same as Ziterdes) and it's a pleasure to work with. The foam is very light, easy to store and to transport, hard enough to take a beating and you can cut it with a knife or a fine saw. Superior to resin or mdf buildings. Very easy to do minor conversions.
I never liked them in the shop or in the catalog but I had the chance to take a closer look (at the Thomarillion trade stand at a convention) and I was reeeeally impressed!
The only problem for me is that the detail level of these buildings is so good my home made buildings look poor compared to them.