Whilst not doubting pr00nes memory for one moment, the name 631 RSU (Radar Signals Unit) seems to ring a faint bell. In the 80's they lived on the ridge to the north of Gutersloh at Borgholzhausen (in an old Dutch Nike site). I went to visit them once or twice and sat in the radar vans as they played with German Tornado's over the Ruhr.
It was definitely 735 RBSU in 1983. I was posted to 721 RBSU that year, at Spadeadam.
FB