Hi guys,
After a last minute trip away I got back to this issue.
After switching on electrics I noticed dash lights were very dim, and, as predicted, once key turned with headlights on they pretty much went out.
Luckily there is enough juice to arm/disarm the alarm (not that there is anything in it worth stealing an they cannot drive it away) so now just need to get a friend to jump the car and drive until it recharges or perhaps it's simply time for a new batt.
Oh and it this should help anyone else reading, I heard a clicking sound coming from the fuse box area with the ignition on.
Thanks