Hi markh, I think the splitter that ethandron is talking about is one that plugs in to the mains and is a booster too. You plug your main coax into the booster then put separate coax for each tv into the other sockets that it has. That way you are not cutting down on the signal strength as you would do with a normal splitter as heathfield says.
Also make sure that the aerial booster you buy is compatable with the new digital signal as you don't want to buy a new booster and find it's not suitable for digital tv.....