replace battery
Dave I recon your battery has cooked it self!
constant charge and discharge " so called " battery conditioning, just wipes the battery out over time!
Some Optimates (although they wont agree) develop faults and even though the "trafFic" lights on the optimate show ,OK, dead , or whatever, It's not always a true sign !
If it's jumping off your car and not under it's own battery steam, then you can bet your battery is boloxed !
try a mates battery before you spend any Dosh!
hope this helps
mav