Mothercare has the reusuable swim nappies too.
We use the huggies swim nappies from PNS, been fine so far.
Swimsuits- so hot here at the moment I would say an all in one solar suit is the best choice. I have some from Aussie Cossie, and one from the baby shop in DB. But they also have in B2B, Wing On, Marks and Spencer and probably Mothercare too.
I know you can also buy them in the markets but if you buy them in the markets you don't have the gurantee that they are what they say they are- i.e. that the solar suit is a solar suit and has the protection from the sun. (like buying cheap sunglasses!)