try Elecsol, they have carbon fibre plates and come with a 5 yaer warranty, and they still provide home delivery. Don't forget that to achieve best charge a leisure battery needs to go to about 14.5 volts, whereasa lot of van chargers paek out at 13.5 volts. New Swifts are now being fitted witha 2 stage charger. If you charge off the van then a 3 stage is recommended. If you do a Goggle search on Battery Chargers then you will also find good info on the charging requirements for various battery types. Also Practical Caravan did an article some while back on batteries and chargers.
For most times amphours may not seem a problem but trying to use your mover ona wet CL after a weekend on battery is when the weak points become clear.