Help with Trike

Hi Everyone !!!!
This is my first post.
This is a great friendly site full of threads of real interest and humour. I like it !!!

Down to business....(forgive me if I am posting in the wrong section)
I have been given a Pashley Picador Trike Tricycle. I dont have a problem with refurbishing the frame but...........
The two rear wheels are in a very sorry state:
a couple of broken spokes on each wheel
Terrible rust on the rims - rubbing off leaves bare metal
I would like to replace them, can I do this with two BMX hubs and rims??
How do the existing wheels come off?
Taken a hub nut & the washers (rings) off and the complete wheel seems to be fixed or stuck to the axle which appears to be threaded. I don't want to damage the axle by forcing anything .
Any help would be greatly appreciated.
Thanks Yanto Twenty