Dreamland double electric under-blanket with separate controls for left & right sides. It is quite old but working. Please only contact me if genuinely interested (this is second re-post after three time-wasters) and you understand the safety advice below.
I think I had it tested a few years ago and it has been used very little since if at all, but you take it at your own risk. The Fire Service periodically offers free electric blanket testing locally. Note, electric underblankets are not designed to be slept on while switched on.
Double electric under-blanket (llandrindod wells)