You can sqeeze a 110 on the battery tray.
Bosch S5 110mah from Europarts
Looking on fleabay all of the 110ah say leisure battery can i asume these wont have the amps to turn the freebje over?
My issue is in and out of than hippo all day some days (nature of the job) and it can be a heavy drain especially with the bloody single point entry, i havd flattened the battdry on a couple occasions when ive been inside messing without the engine running (gladly only while ivd been at home) prime example when i moved my switches to the cubby box windows up and down testing etc the battery drained too quickly imo..I agree with John T - the CCA rating (cold cranking amps) is much more important that the capacity (Ah). I bought a cheap (£55) YUASA battery for my Disco 300 Tdi a few years ago and although it has never failed to start, on a cold frosty morning the engine turns over worryingly slowly. Very slowly in fact. I thought it might be the starter so I tried a Bosch S5 from another and it felt as though it was going to turn the engine around whilst still in the car...
The capacity (Ah) is only really important if you are going to be using a lot of high-drain electrical accessories.
Hence if you are budget conscious I would suggest do your research and go for a higher CCA rather than Ah.