Thanks for all the useful info and advice. My old battery is 6 years old now, and the top part is starting to crack at the cell joints, so time for a new one. I will definately keep the old case, as it looks just like an original supplied one, so could be utilised as suggested. Searching around, it seems some companies will not deliver a battery with acid, whilst others do not have a problem, so it looks like I will be asking one of them to supply my next one.