All,
Following on from my other emails yesterday, last night I restarted everything again only this time the U2 and GPS were switched off for an hour or so while I worked GB70DAM on 40m.
Once I started it up and the GPS locked, the clock once again was showing 00:00:00. I inverted the input and the time showed correctly.
Today, over 12 hours later, it's still correct to the second! Compare that to yesterday when it was rapidly losing time.
73 Keith, G6NHU