Go for the CTEK or Ring chargers. They are both excellent. I found Amazon was the cheapest place for the Ring Charger I bought. They can charge and maintain a battery so there is no worry about it overcharging etc.
As for the battery you can get a 100AH on ebay for £70 (
http://www.ebay.co.uk/itm/260963030359) or for around £55 (
http://www.ebay.co.uk/itm/190516260577) you can pick up a smaller 85Ah. If you are just charging lipos then you will probably get away with the smaller and lighter 85Ah.