I made the classic move from booking office to Divisional Movements office in 1970, working at DM Euston in Eversholt St. There was, as mentioned, a BRSA club in the same yard as Collectors Corner and it was soon suggested that I join by paybill deduction which I did, and duly received a membership card. At lunchtimes I used the Euston (BRSA) club and sometimes, if passing in the course of work, one at Willesden (which had a particularly officious door man). Curiously, however, the BRSA was not affiliated to the CIU which meant that one could not access other Working Men's Clubs (which were almost all CIU affiliated, denoted usually by a prominent sign outside) using the BRSA membership card - to enter these, one had to be the guest of a member.
There was then a railwaymen's club in Northampton with two branches. This was not, however, a BRSA club but was (from memory) called the Northampton LMRCA and it WAS CIU affiliated. This meant that, ironically, as a member of the BRSA I couldn't use it except as a guest of a member, although members of other trades' WMCs could. I am not sure whether 'LMRCA' was another organisation with a geographic spread, or just a name used by the Northampton branch. I am fairly certain that the Northampton branch near to the station is still operating.
Mention has been made of the club below Euston Station; I remember this well, and will give details without further comment. It was called the Griffin Bar (or maybe Club) and was provided by BR, who subsidised bar prices. Perhaps by coincidence, the Euston S.M. at that time was Mr Griffin (perhaps he was the licensee) and there was a sign outside that read 'Only staff on duty may use this facility'...