Thanks for the comments and suggestions everyone. Albert, I have been wondering if the IR remote was going to work for the reason you mention. Like you though I'm reluctant to walk around outside with the compartment door open exposing the connections to the elements and there is the additional risk of catching the door and breaking it off the camera. I'm hoping I can set the IR forward enough on the supporting arm to make it work.
I am also wondering about whether the trigger on the lens holder can be set up to effectively work the IR button Steinback. Anyhow I thought I'd give it a try. I've ordered a Pentax one. If it doesn't work I may have to go the cable release route.
Thanks for the tips Terry. I did come across this DIY site myself:
DIY Cable Release
Not sure I'm up to the tech diy stuff, but if the IR remote solution doesn't work perhaps I'll have another look.
Paul