I have an 07 plate MX5 i bought just over a year ago. Up to now I have had no paint issues but I have just noticed that a couple of areas have come out in what I can best describe as a series of small pimples. They do vary slightly in size. The p[aint finish in those areas was perfect up untikl recently and I had no cause to think that any repainting had taken place but I wonder if there has been some sort of reaction that has taken ages to manifest itself. Any ideas?

It's moisture trapped between the primer/basecoat/lacquer causing microblistering, likely from paintwork carried out in damp/humid conditions, or from waterbased basecoat which has been incorrectly or insufficiently dried.

It's common on smart repairs, insurance quality repairs, and can take several years to become noticable.

Dave

As Dave says its probably had a smart repair

Not on the boot lid/around the rear number plate light by any chance ?

MX5's have so many rust issues anyway your doing well not to need welding by now if it hasn't already. Rear arch, sills and the whole underside are huge problem areas, you really need to keep on top of it or it will just dissolve away

No, its just in front of the filler cap and on the top deck that the brake light is attached to.