You can get towbars new online quite easily, they are not too bad to fit to on a V40 just one bolt near exhaust is awkward and the wiring if you are just going for basic 7 pin not too complicated. There is somewhere on here a diagram. There should already be a plug in the boot where you can pick up a dedicated power line.
I would fit a bypass relay as it avoids any issues with car lights.
see
https://www.pfjones.co.uk/v40-estate...ge-towbar.html
However by the time you add up the towbar and electrics its nearly £150+ so not a huge saving and at least with your quote of £250 if anything goes wrong you can go back and ask for it to be fixed.