hello

I hope I can get some advice: I'm very new to beekeeping, having started two nucs this spring (in the UK (North Wales) in British National hives). I decided to go foundationless (not a lot of support in the local beekeeping community for that) and so far everything as gone great - both hives filled their brood boxes with beautiful straight comb on the empty frames I added inbetween drawn nuc frames (with turned over wedges as guide strips)
Unfortunately things went a bit wrong after putting on the supers - in 10 days they built a lot of comb in there (during a great spell of warm weather) but it's all a big mess, with wavy comb built vertically across the frames, started from the bottom, not the top.
I read up on some relevant posts here, and I see that my biggest mistake was to not provide a ladder for the bees up the empty super frames.
Also I have no drawn shallow comb to use in the supers as guides, and I have also read here that alternating empty frames with (wax) foundation is not going to work either, so I'm a bit at a loss at what to do.
Will one (wax) foundation frame in the middle work as a ladder? Looking at the mess I have this will hardly be enough to entice them to build straight comb throughout the empty box. Or should I fill the super with foundation for them to draw out so I have a 'starter supply' of straight drawn frames that I can rotate out at a later stage?
Would be very grateful for any advice or suggestions.

Katerina