As promised, here is a video of the enemy AI starting to work. I've only just started and there are still some bugs in the heuristic, it moves into positions where a piece is threatened where it should not. And it doesn't yet have any concept of check, check mate and en passant and castling, and exchanging pawns.
The lookahead is only 1 move so far so it isn't that intelligent, but I wanted to post this as I may be busy with shopping etc before I can improve things. I'll also try and get some menus in soon to build a framework for the game.