In message , David
writes

Chanced across a small blow up one in HomeBase for £4.99 which seemed
worth a punt.

There are a million blow up pools available via eBay. Sounds like a
good idea, as you could stand the pot on the base then inflate the sides
around it, which would avoid having to lift the pot over the inflated
sides.

My suggestion was going to be a rigid cement mixing tray. More
expensive, and fairly shallow, but also useful for other jobs - like
mixing cement :-)
--
Graeme