An aerial in the loft might work if you're not far from the transmitter and the route is otherwise unobstructed. But you'll be much better off with an outdoor one instead. If you have a good signal then you can just use a splitter but you can always use a distribution amplifier. These are like an aerial booster combined with a splitter and are not expensive. While you are at it, why not combine the TV signal with the FM and DAB ones too. If you want to be really clever you can also add the output from your STB so you can watch cable/satellite around the house too. For this you'll need a 'loftbox' or something similar.
There's some useful info here:
http://www.bbc.co.uk/reception/factsheets/index.shtml