Just came across this site after a google search for Brian Thomas. I see on the opening page a picture of the Royal Signals badge with Berlin above it credited to Brian.
A Brian Thomas was my detachment commander circa 1970-71 in Radio Troop 229 Signal Squadron. A fine and thoroughly decent chap. He wrote to me soon after I left the army. Unfortunately having just started a very demanding job I was a little slow responding. My letter was returned unopened marked as unknown at the address he had given, (a barracks in the UK).
Since then via Friends Reunited etc I have tried to find him without success.