Losi starter box
 

Just after some advice i after a 12v gel batt and just wondering what size i will need and where to get it from

You want a 12v 7amp hour,This is the one i used in my SMD starter box before going over to lipo...
http://www.screwfix.com/p/sealed-lea...equestid=76251



It was a good fit in my SMD box, just make sure you take the dimensions of the battery down and make sure it will fit inside your box before you purchase it.