mondeo 2001 tdi died?

have had my car for 5 yrs with absolutely no probs at all. suddenly would not turn over (although still opened with remote key)
battery tested and found to be ok. jump started and used car
next day, same thing in the morning.
rac fitted new battery (although old one seemed ok on tester). started at 11.30am next day but then nothing at midday!
took to garage who said the battery was u/s and fitted new one. said there was nothing wrong with electrics.
worked for 3 days and then same thing.
garage have now washed their hands and told me to go to ford dealer for diagnostic.
phoned ford garage who have advised me to first remove the ford radio and see how long the car will start for as apparantly in 8 out of 10 electrical problems it is the redio causing the battery to drain.
took that out yesterday and so far car still starting but wont hold my breath.
any suggetions would be welcome