Just to bring my input for this thread to a close. Spent ages searchng for local garages using Autologic. Found a couple but when I mentioned the specific problem it sounded like they didn't have a clue! Decided not to risk any more costly mistakes so bit the bullet and booked it into E+E for this morning. About an hour and half drive from Dagenham so could have been worse! Met a chap there who had driven down from Liverpool for exactly the same fix. As mentioned above, 15 minutes later I was on my way back home , £90 lighter but problem fixed. So much for getting a cheap battery! Still, lesson learned. Now to start looking for that BMW I fancy!