They can't even READ any details, let alone store them, they are a simple doppler effect gun, the plod car would have been there for two reasons, 1 being that they have to test the gun that day with a car with a calibrated speedo against the gun, otherwise evidence is inadmissible, two to chase any people that were naughty enough.
bearing in mind most speedos over read a bit you were more likely doing a real 42/43, so they won't be interested as this is even below suggested limits of 3mph + 10% which is what most forces allow, though there is nothing set as a rule.
tabetha