Less than straight forward to diagnose is what I hear. Tried replacement battery, is there anything else to check before I stump up the thick end of £600?

 

surely you have a voltage meter ? hook it up to your battery, note the voltage (should be around 12V) start your car and go look at the meter, (should be between 13.5 and 14.3 V) If the meter did not change or is below 13.5 you need a new alternator.

 

When mine went on my 02 S, it was pretty easy.

Killed a battery.

New battery worked for a day, and then all sorts of strange electrical things started happening. Dash lights coming on for no reason, radio going on and off, and then the car died.

$700 or so to fix.