Giles has spent a lot of time, money and effort getting things together, which has shamed me into at least contributing something, despite my lack of terrain building skills. And so, scraping together whatever odds and ends I could find, I started making some walls - something that we'll need a lot of!
First off I used some old strips of packing foam to make some rough stone walls. I glued the foam to some strips of card, coated them with PVA glue (adding the occasional lumps of dried up Milliput), painted them grey, washed them with Quickshade and matt varnished them.
The results aren't perfect, but not too bad for a first timer!
The next lot of walls came about after I discovered the excellent Paper Brick website, which allows you to choose from a wide variety of brick styles, mortar colours and layouts, that you can then print out.
So I made some basic walls out of cardboard, printed out some bricks and glued them on. Very quick, easy and, if you squint a bit, not too shabby!