The steppers, the studding (threaded rod), the coupling nuts, the new ICs to power the steppers and the perspex all came by post from eBay sellers. The rest, I picked up from B&Q, and was surprised that it's not all that overly priced.
Working from a plan inspired by the video on how a guy built a CNC from plumbing, I cut, drilled, bolted, and filed until I ended up with an XY bed.
Adding the steppers with aluminium mounts and sticking the locking nuts to the beds with polymorph (polycaprolactone) and superglue (krazy glue or cyanoacrylate for non-US) meant I could test out the steppers.
The only fail so far has been the stepper motors not being gripped enough by the nuts even though they are filled with polymorph and then superglued on. I guess I will have to wait for the taps and dies to arrive so I can make properly grub screw locking connector collars for the stepper shafts and the studding.