The spindle is still a significant proportion of the total weight of the things you have purchased, so the postage would have been a bit cheaper without it. Plus you can use best offer with some of the sellers on eBay to get the spindle for less than £252, so overall it's likely to work out cheaper. Even better, get the spindle on ali-express as there it is cheaper than any of the eBay sellers.

I'm not sure if Chai is still the cheapest for rails and ballscrews either since there are plenty of sellers on ali-express with them. Still, he's very easy to communicate with which does help.

What are you planning on using for the bed of the machine? In the drawing it looks like wood...which is fine if you're mainly machining wood and plastics.