So another update on this, went back to the place that did my tracking originally and they asked for another go at tracking it.
Don't know what happened the first time round as the before settings this time round were waaaay off, the after looked good though and driving down the road all felt normal again
Need to get a retest date now for the side slip test.
So on a quick check I'm still getting some vibration at motorway speeds but with your comment above burnt into my brain I did a bit of testing and on braking gently from 30mph there's the tinest vibration in the steering wheel.
So thought stuck caliper (or maybe guide pins but the mr2 doesn't have guide pins) and with the two wheels up in the air the left wheel spun alot free-er than the right wheel so I started on the right. Took off the caliper and worked the pistons in and out a few times while coating them with a bit of silicone grease when they were fairly extended.
Put it all back together, pumped the pedal and then spun the disc, that's when I noticed a tight spot while it spun. With everything removed bar the disc I can see it warped by eye which I'd consider a serious amount of warpage. It's either that or the wheel bearings are installed at a slight angle which I'm hoping they're not given theres only about 1000 miles on them.
I swapped the discs over and the problem moved with the disc, so I'm presuming it is the discs and so have ordered replacement fronts. I've tried wire brush dremelling the back of the disc and hub but that made no difference.
Parts are due on Tuesday so hopefully that sorts me once and for all