Well I figured since I've had other topics asking questions etc, the proper thing to do would be to collate pics & info onto a proper build thread really.
Might prove more useful potentially for someone else in future that way (as an example of how not to do things!!).

I've had my X2 for many years now but always loved the idea of converting it. Recently I took the plunge so here is a bit of the story so far.

The first thing I did really was to establish what electronics to buy. Budget is a big (small) constraint for me as I have very little spare and any 'spending' money for fun stuff can be sporadic at best.
It means I have to go with cheap as while I agree with the sentiment of "Save up a bit more and get the better one - you'll be glad you did", I never know when I might get a few extra quid or whether it could be ages, thus I have to make do, and then potentially improve/upgrade in future.

With that in mind I ordered a cheap kit from ebay china after some research.
【Germany SHIP】3 Axis NEMA 23 Stepper Motor 435oz in Single Shaft 4LEADS CNC | eBay

Shortly followed by a 230mm ballscrew (about £15), a 400mm ballscrew (about £25), 3 stepper brackets (£33), and 2 of 8mm x 10mm couplers (about £10).

The Y axis was pretty easy to rough fit, following removal of some material as marked from the saddle:
Attachment 239644

Getting the X axis to fit on the other hand has been much harder.
The ballnut now has been horribly brutalised and looks like this as a result:

Attachment 239646

But it's almost the right fit now.
This is combined with a lot of grinding out of the saddle to help the ballnut sit low enough.

Tonight's task was to see how the end of the new X ballscrew would need to be dealt with.
The original leadscrew has a fair bit of length protruding from the end cap & thrust bearings (which I had to use a puller to remove!!).

Unfortunately while the end of the new screw was the same 10mm diameter, this only went back half an inch or so then had a wider threaded section, before stepping to a 12mm diameter section. No use!

Here's what I therefore had to do.

Attachment 239648

Turning the wider and threaded sections down to 10mm was not easy. I had to use the fixed steady but the proximity of the carriage to the steady meant that I had to put the cutting tool at a horrible angle with way more of it sticking out from the toolpost than I should have done. Obviously this resulted in loads of chatter etc, and a rough finish. Once I got it more or less right I then had to spend a while smoothing it by hand.

The outcome however is that the X ballscrew now more or less fits through the end cap correctly and goes through the thrust bearings reasonably well.

Attachment 239650

With the X gib strip in place the ballscrew is a bit tight and I think has tension on it that needs addressing. I think I need to grind a bit more metal off somewhere, but not 100% sure exactly where, in order to allow it to more freely.

One thing I'm not sure about though, is whether I should use a support bearing at the opposite end of the ballscrew to the stepper, ie this end here:

Attachment 239652

Any thoughts on this are welcome. I presume it's not 'necessary', but will it give much benefit if I get and fit something?

Really enjoying this project now that I have some progress. Can't wait to get further.
Thanks for all input so far from you guys. It's very much appreciated.