Ah Roger, I'll see your "Wheels on the bus" and raise you "London Bridge is falling down."
This was played on a plastic disk which slotted into a toy train which trundled over the carpet as it played.
Sounded (not sung) like "London bridge is falling down - choo choo - choo choo" and so on, and on.
My oldest son loved it, there were other disks but London bridge was THE one for him.
I shamefully admit to hiding the batteries, sorry Gavin.
Oh God it's for sale on Fleabay.
Tomy The Tuneyville Choo Choo Train Toy