By the sounds of it Gav, you wanna play games in using a TV card on the same machine. Do I read you right?
I think everyone here is suggesting connecting another Amiga through your TV card.
If you want to use WHDLoad to play games, unfortunately, WHD has to lock off the whole system (Temporarily 'killing' workbench. I've never heard of a way to get an Amiga to display 2 signals at a time (Workbench through a GFX card & ECS/AGA at the same time.
Hope I've got the right end of the stick.
FuZion.