Have got a 16 year old Jap hatchback.  It's probably got about a 
year's life left in it.

The battery has started playing up and is now not taking much charge 
(with external charger or on the car).

New basic battery at Halfords is 50 but it's not worth spending 
anything like that for a car which be scrap in a year or so.

So where's the best place to get a cheap used battery which will see 
me through for a year or so?