Didnt realise the cars werent booked in either, I assumed the mechanic had the sense to at least make sure the paper trail looked right, clearly I gave him too much credit.

Yes then, possibly they might be able to look into it, I still doubt they will though, as its too much hassle for too little gain for them and they cant rule at a later date if an MOT was valid or not, so the most they could do really is request a retest for those cars I suppose, but I dont think there is a rule that allows them to even do that.

I wouldnt worry personally, you can easily claim to have acted in good faith IMHO (assuming you have such a car!)