Well I think I can officially close this thread as my tank is currently zeroing ammonia & nitrite in 12 hrs!!!
I don't really know why the cycle stalled tbh, I think the only possible answer is that maybe I let the nitrates spike too high (but that's just a guess).
Anyway, I'll post in the thread I originally started below and post some pics in there for anyone interested.
Great news Welsh!
I got some amano shrimp for the betta tank today and they don't half munch and munch and munch! lol
What kind are you getting or is that all in the new thread? I'd better go and have a look!