Welcome to the Carver Site!!
I'm kind of reading behind the lines, sounds like these units were maybe operating in a 120v location then they moved to the UK?
On the C-1 have you taken a look inside? Some have a switch (SW15) near the power supply.
Switch in question - Black item, far right center below white card on top of power supply.
If the C-1 has this switch already installed then maybe at least the C-1 has a chance of being restored and upgraded by Nelion.
The type of plug will also need to be looked at. What type do both have? US or European?
As for the C-4000 I have no Idea if it has a similar switch.
While not the most elegant of options it does sound like a Step-up transformer might be the first option? Maybe.
When you get 5 or more likes please post some pictures.