Didn't know they did this, or we'd have tried it for our 40+ year old one. Instead I coughed up for a new one, which was quite a few bob and some of the attachements use a different connection now, so after that lot had been replaced I was a few hundred quid poorer. The new one doesn't LOOK as well built, but I think it probably is in reality, and yes, the motor and speed control is much better.
Presumably the new ones aren't built in Havant like the old one was. I used to know the service manager for Kenwood, till he retired and moved away, and as they were closing down the local operation (we're about 2 miles from the factory) we got some very good prices on spares for other models that friends had.
If I was in your situation I think I'd for for the refurb, I think the basic structure of the chef will still be there, with a few old Volvos and BMW flat twin motorcycles, after the final nuclear holocaust.