Michael Sheard published his autobiography "Yes, Mr Bronson" in 1997. Space: 1999 is mentioned by pages 42-43.
Space 1999 was to have been a very big tele-break for me, but the American stars, Martin Landau and his wife Barbara Pain - sorry, Bain - felt that there were too many regulars taking up too much of their screen time, so a number of us were axed. We were all blown up at the end of the first episode! For some reason I made a return visit some fifteen episodes later, don't ask me why. I know it now has a cult following - it's out on video and we're all still making money from it - but it was a terrible series.
One fun thing I do remember, however, is a lady member of the production staff going round the studio with a roll of sticking plaster and a pair of scissors. All the women - and I mean all, extrabums and starbums alike, there were no exceptions - had to stand to attention with their chests thrust out. And if there was the slightest outline of a nipple showing through their futuristic woollen costumes, as there invariably was, they were led by the hand round the back of the set and the sticking plaster was used to good effect. The only lady who didn't need the sticking plaster treatment was Mrs Landau - Miss Bain. The suggestion being that she was far too professional!
A second autobiography "Yes Admiral" was published in 1999 and focussed on science fiction roles and conventions. Space: 1999 is mentioned in passing several times, with a nice appreciation of Barry Morse when they met at different conventions (p168-169).