Any idea how to clean a memory foam topped mattress?

[TheChicOfIt]

It's a normal pocket sprung mattress, but it has a memory foam top which is sewn into the mattress so can't be removed.

Sponging it doesn't really work.

Anyone got one or got any ideas?

I am wondering about this. Do you think they cab be steam cleaned?

I'm not sure? TBH it seemed a great idea at the time but in hindsight I wish we had bought a normal (and much less expensive) pocket sprung mattress!!