I have now been able to take more of a look at the wheels. The one that was flagged as distorted in the MOT has a big dent on the inside edge, originally I said it looked fine because it does from the outside, I could only see the distortion by jacking up the car getting under and spinning the wheel. So I swapped it for the space saver and the judder pretty much went away, there is still a slight judder but only really noticeable if you are actively looking for it, I suspect there is a very minor issue with one of the other wheels. So I thought I had found the issue and the bent wheel is at fault, but just to make sure I put the bad wheel back on and put the space saver on the other side taking off a 'good' wheel, but when test test driving the issue didn't come back. Suggesting that the solution is just to have a the space saver fitted regardless of which wheel is removed. Now I've put all the normal wheels back on the car and the vibration hasn't really come back. It is there but not that bad.. Like the wheels have seen the space saver and realise they may get swapped at any point so are now behaving themselves. So I'm guessing that there are multiple wheels causing an issue and when the issues are 'in phase' the judder is pretty bad. Really strange though as I have swapped wheels around on the car loads and the issue has stayed pretty constant.
Where should I go from here? I could try and get a wheel off ebay see if that helps, but no guarantee that the one I'm buying isn't also buckled. Or maybe I could send off the wheels for refurb, I have seen they can sort buckled wheels, I'm not really bothered by aesthetics of the wheels and with wheel refurb companies their main gaol is to make the wheels look good and can sort any buckling in the process which means I could be paying a fair amount. Any suggestions of companies? Or I could go for new after market (cheap as poss) set of alloys?