The incorrect leadscrew is in my opinion not the leadscrew, but one of the Spindles in X or Z. Eventually the machine was sold as imperial and a damaged spindle was changed with a metric or vice versa, but without changing the dials as well.
If you are not sure with the machine, take a dial indicator (with large foot instead of ballpoint) and holder and a long guide shaft and test, if the machine is ok. check the gear for speed and feed, the guides the backlash and the levers for engaging the feed and leadscrew.

Normally I say, if you get a machine that is big enough
for your job and new with guarantee, take this. But the colchester is the same price and a much more rigid and powerful machine like the little chinese.

If I want believe tony's website, then the machine from Ebay is a bantam 1600, but they can run 2000 turns, maybe thats the reason for the other name. The other 2000 in reality a harrison looks completely different.