Thanks Ade!
This helps me a lot! Topping it up seems a great idear to me 
What kind of DRO are you installing, there are o lot of them out there to buy.
Hi Dennis,
I bought this Ditron one:
https://www.aliexpress.com/item/32951659566.html (with the RPM option which, strangely, is far more expensive than the without.... that wasn't an option when I bought it)
I went with 1uM scales (all optical), which works great - although the 3rd decimal digit tends to flicker when the lathe is running... too much vibration. I wanted 4 axes so as well as the carriage and the cross-slide, I have one on the top slide, and I would like to fit one to the tailstock but haven't got a Round Tuit yet.
To say it's transformed the machine is an understatement! It's absolutely brilliant... and also showed up where I have a fair bit of wear in the cross-slide leadscrew... which would explain why I always had to work so hard to hit a dimension before I got it.
Mounting was "challenging".... particularly on the topslide where there's not a lot of headroom. I ended up milling my own brackets from lumps of aluminium and/or steel I had lying around; and even so I still need to fettle the cross slide end cap, as I can't rotate the top slide because it fouls the bottom of the readout. 30 seconds with an angle grinder will solve that... but it's cooold out there...
I also put the main readout on the front (it would be better on the back) - mainly because access to the back of the machine is highly restricted, and I'm buggered if I'm moving it on my own again.
The Ditron package comes with covers, various brackets, the slides cut to the correct lengths (I just worked mine out based on how far I could move stuff - if I can find the original order, I'd be happy to send those lengths to you). I'll grab some pictures too... because I realise I haven't done that (and I really ought to).