Ray,
It just so happens that I covered another 200 miles and I got the 3 beeps once and it came up with the gearbox overheat warning as well., it flashed up for less than a second when I was sitting at about 70 in traffic in the fast lane, so I never had a chance to investigate or stop and I compelted another 100 miles without getting the warning again so I think it might be the same as your one. I will investigate the electrics when I return from work in couple of weeks.
Thanks for the replies.