Thanks all - Rosebud, Xantham gum does seem to present itself as a good alternative. I just need to find out if I can get hold of it.

Ground almonds may be worth a look.

Cream is great for thickening a sauce - I did that with a chicken curry last night and it worked perfectly. But for a thick base to a stew/casserole, there's just too much liquid in the first place.

I'll report back if/when I find the best solution.