As I say, I had severe judder moving from rest. Fitting a new one of these stopped it...
https://www.lrdirect.com/KKB102480-Bracket-Engine/
Mine's a '99. The same part for a MY01+ car is this...
https://www.lrdirect.com/KKB103190-Mounting-Engine/
The issue was solved immediately by fitting the mount and came back immediately I put the original back on - so it did have an affect. I don't know if yours is suffering the same problem - but you mentioned problems with your mount - so its very coincidental!
The 2nd time I did it, it probably only took 30 minutes to swap over and the early part is only £17 for a Britpart part to see if it helps. The later one starts at £40 so quite a bit more costly to take a punt on.
I've also hear that leaking oil that gets onto clutch plates can cause this. I also wonder whether a sticking release arm (precursor to seizing!) could also cause it.
All clutch components need careful lubrication, including the release arm spindle.
I use moly based grease on all PG1 release mechanism parts and it seems to work.
There was actually a Rover TSB on the PG1 box and it's judder way back in the late 90s. It explains how a dealer technician can spray a dry PTFE type lubricant on various components to stop the judder. If that fails, then a full strip, clean, lube and rebuild are needed.
This judder affected many PG1 boxes, including the Honda box the PG1 was based on.
I developed my own cure for the MGF and ZS180 which suffered the same issue. I'll dig out some pictures of where to lubricate tomorrow when I've access to my data drive.