Typical 'leisure' batteries aren't really suitable for high load cranking, they're more of a slow discharge/re-charge type of unit, designed to run lights, water pumps, etc in caravans over a weekend away where no mains connection is available. This is why they have a generally high Ah capacity, but a low Cold Cranking Amps (CCA) rating.
A really good compromise is the Numax CXV24MF, which has enormous 900 CCA and a relatively high 86Ah in a small enough casing to fit in a red battery box:
Numax CXV24MF Heavy Duty Maintenance Free Leisure Marine Battery 86 Ah 900 CCA | eBay
I've run a few of these over the last 5 years and they've been excellent.