Kev,
I used 85 amp leisure ,but with short journeys had to mains charge every 2/3 weeks or so,only do about 3000 miles a year.
So,leisure died,replaced with battery from 3 litre jag about 6 months ago and never had to bring inside to charge,got relay obviously.
Battery was given to me by a customer,but if you try a friendly garage thay may swap batteries with you or sell one to you.
They need to account for any batteries they dispose of so can just swap yours for theres.
Good time now as people replace batteries with not enough startin amps for car but still loads of life left to power pumps