This morning I caught them doing the mating dance (I knew female was carrying eggs, but having read that they are really difficult to breed thought nothing of it) so I moved the pair to my q tank where the proceed to lay loads of eggs. I really hope I get a couple of fry from them as I was planning on buying some more anyway. The other female is looking ready to spawn too so keeping an eye on her too.
Also I've bought myself a 370 litre tank with all the filters/heaters etc for £50 so starting to set that up too :-) so even if all the eggs survive, there's plenty of room for them.