Well done Watson, that is most interesting!
Heli1: Even in John's 'super-duper' size image I can't make out the number on the Hiller .. except (perhaps) the orange nose numbers which (I think) are either 46 or 47!
More Hiller ..
Bristow Hiller UH12E G-ATDW as seen at Southampton's Eastleigh Airport in 1967 (Photo: Barry Friend)
Seen here wearing 'Plessey' titles. That seems to have been a long-running contract for Bristows despite the fact that it was held on and off by a small number of additional operators. I believe it was 1975-6 when Ferranti had the contract which had been taken over from Mann's after the incident involving the ill-fated G-AXAY in 1974.
A year on from the above photo this craft was sold to New Zealand where she flew as ZK-HCQ.