Thank you for this, you have helped me confirm the correct rabbit hole.
Most sources point to 1 Balloon Centre as being purely barrage balloons but I have my man there from 16 May 1941 until he goes to Kilkeel in February 1942.
As you point out he passed his trade exam in December 1941 so the dates point to him having qualified at the Balloon Centre.
I don't have any dates to differentiate between Skegness & Kidbrooke.
He left Cardton in April 1941, briefly passed through Skegness and by May 1941 he was at the Balloon centre where he qualified in December and was posted to Kilkeel February 1942.
Thanks again for all your help. I was thrown off track by the Balloon Centre but you have come up with a plausible explanation.
Added
After a little more digging,
"A very important unit based at Kidbrooke was No 2 Installation Unit. From 1939, this was responsible for constructing, maintaining and repairing all of the Chain Home radar station masts around the UK coasts throughout WW-2"