Thanks JethroUK ! ... eventually got to this page ..
http://www.redremote.co.uk/ ..
which although it looks a bit dated, seems to have loads of info about remotes and signalling and stuff like that .. very useful!
Another question springs to mind though .. Guide+ information depends on an analog signal (as I understand it?) .. given that analog is gradually being phased out, is there much point in using it?
Thanks again ...