you need a charger that specifically says it is also suitable for sealed lead acid. they charge at a slightly lower voltage.
I have one of these.
http://www.argos.co.uk/static/Produc...er/7402096.htm
edit that charger is a bit too powerful on full charge i put it on trickle and leave it
this will do fine and is a lot cheaper
http://www.argos.co.uk/static/Produc...uctInformation