Please do keep us posted as I think I'll need to change the battery in mine at the end of the 'summer.'
Went to City Auto Components as kindly posted above.
Can't think of the brand just now as I'm at work, I didn't name drop, feel a bit odd doing
but the chap behind the counter was very helpful.
I picked up a new 72AH battery, which was stronger than the one which had died (66AH)
for 79 euro.
I have a 156 JTD Multijet Diesel and the engine cover is a pain in the arse because it limits the access to the battery.
The tricky bit is opening the battery strap which is tightened with one single nut which you will need a 13mm socket to open but you will also need a long ratchet arm to get to it so you can open it and be careful because it's very easy to drop both the nut and/or the socket when you get it off.
After that it's very easy, a similiar size spanner will open the terminal connectors and after that Robert is your father's brother.
Slip in the new battery and connect up.
It took me about 20 mins because it's hard to get your hands into the small spaces the Alfa guys have supplied but it could probably be done quicker.
All done now anyway and she's starting like a dream.