Thanks ladies - I can look up the Nigella recipe for the ginger + lemon cake, thanks for the pointer, Habbibu. Any tips for a foolproof Brownie recipe?
Now I know the MN recipe for choc chip cookies is good, I can look that up too, thanks prettybird - doesn't matter they are not cakes, I probably should have said "bakesale" but I wanted to include things I didn't have to bake 
Blondie - although I love it, I've never made millionaires - always seems a bit time consuming to me, with having to make shortbread, then fudgey/caramely layer, then chocolate... am wondering if it's a good return on time invested?
Thank Ruprekt - In the past we've always done "fairy cakes that appeal to children" with coloured sprinkles or chocolate buttons. That's def. where I'm starting from (should have said in OP, sorry), just looking for other things as well
Dilidali - Interesting.... but, in your experience, is the "profit" from a whole cake anywhere near the "profit" from slices, or small cakes?
Any more thoughts, very, very welcome 