So then, thanks in part to the man above, the car is now fixed, wahoo.
As per usual, I could have fixed it far cheaper by replacing just the one inner CV joint, but it simply made more sense to replace both the drive shafts. Yes, it did cost me a few hundred more, but the job was easier and considerably less messy lol ... I always believe that if you're gonna do a job, you might as well do it properly!!
Did the drivers side 1st, bit of play in the joint, but nothing major, & certainly didn't cure the terrible shaking I was getting under load!! Decided to get the hole car up in the air & run it in gear just to confirm where the vibration was (bit spooky seeing the car levitating & doing 20mph on the driveway lol), but that definitely pointed to the passenger side being goosed. Took it off & pulled it apart to find that the actual ball bearing things inside the cv joint had cracked & separated from the ball joint. Replacement one on and all sorted.
Then I taxed it at lunchtime. Now just need to get the Haldex controller of and the car up for sale properly at some point.
As ever though, the car so good for everyday im not so bothered about when it goes lol.