John..
Sorry can't help you with 705's mounts. By the time that I had traded my push bike for one with a an engine (and hence was able to visit deepest Cornwall.... or Culdrose) 705 were operating the Gazelle.
I have got some nice piccies of 750's Sea Princes though, incl six of them in formation.
Synthetic
Some of my "compatriots" at Roborough were... Ron Barker, Martin Degg, Pete Hawke, Rod Webb, Derek Boyce (saw him at Kemble last week) and Kevin Hemsil (+ all the Brymon People I knew and worked with)
Best rgsd BEX