After following the advice here, and Kevins excellent link information, I think we can safely say the battery is totally knackered.
Summary is this...I put the battery on the bench and checked the voltage....12.47 volts. I then connected to a charger, and it started at 4 amps, this changed to 2 amps within 15 minutes. After an hour, with charger connected and charging, I had a readout of 14.61 volts. I disconnected after a further 30 minutes, Waited an hour, and had a readout of 12.86 volts.
I then attached the battery to the car, connected and had a readout of 12.81 volts.
Getting wifey to crank the car, (which would not turn over), I got a reading under 8 volts. Switching off, the battery returned up to 12.2 volts.
The recipient car was the 2.6 which has no electrical problems.
In the meantime, the battery from the 2.6, which was used to test the charging system on the 2.5, is holding a 12.89 charge after resting overnight, after my 20 mile test run. The car started first time with a high speed turnover. All the idle and 2000rpm and charge readings are within the expected scales. I think this negates the 2.5 systems as causing any battery problems.
Sorry this is a bit long winded but shows how our maintenance guides can be of extreme help

Thanks to all for contributions on this thread
