In theory, not sure if it's possible in uk or dk, you can build a very strong and capable CNC with under £100 by hunting for components in scrap metal yards. You can find good rails, ballscrews, steppers, even servos, sensors, relays, cables, material for the frame, everything, sometimes at the cost of scrap-iron (£0.10?).
But you need very good knowledge of the components you are searching for, and A LOT OF TIME. I'm making a guess here saying 1000 hours (includes getting all the components, documentation, setup, tweaking, modifying, building, etc.). Now calculate how much do you earn for 1000 hours and tell me if it's worth it, in financial terms. On the other hand you'll learn a lot of interesting and useful things along the way.

PS. It's a pity that in our capitalist times a lot of very good components and machines are thrown away. They are no longer reliable in industrial production but still good, sometimes excelent for hobby.