Thanks for your inputs so far guys.
I have had a re-think and decided that I am not going to ruin my RC Hobby by trying to make any money out of it and therefore won't be needing to make large quantities of wing cores. So I won't waste my time, effort and money on building a CNC hotwire machine.

I will however, be building a CNC router although I think I need to build a shed/workshop first. Integral garage directly below my son's bedroom and attached to the living room will restrict the noises I can make.