Many thanks for the response, but it doesn't get as far in as letting me see the Pi booting up. It refuses to switch between VGA and DVI it simply reverts to VGA and the RM logon screen. Have tried switching everything around but the issue appears to be intermittent. i can login using a Pi on one machine, shut it down and it won't work on another PC. Similarly a PC can work for 1 Pi and not the next one I connect to the same PC.
Hope that makes sense!
Mel