Back of the set boosters can work but they aren't normally the best solution and can even make things worse depending on what the problem is. Good practice in weak signal area is to fit a big aerial of the right type as high as possible. Should be mounted outside not in the loft.
If and only if a big aerial still doesn't give a strong enough signal then you can consider a
mast head amplifier (eg a booster mounted at the top of the mast next to the aerial).
There are technical reasons why a mast head amplifier is better than one behind the set. For example it amplifies the signal before it's attenuated by the cable down to the TV. All amplifiers add noise to the signal as well as amplifying it so you have to be sure that a weak signal is the problem and that you already have a good aerial installation before considering one.
If the aerial and the cable from the aerial down to the TV is quite old then consider getting both replaced before you go much further.
> we won't be getting digital in this area until 2012?
Ah I see. Trying to recieve digital TV in an area not due to recieve it is pretty difficult or impossible. If you type your postcode into this site and play with the height option it will give you info on what sort of recieption might be possible. It's quite technical though. Otherwise tell us your full post code (if ok with that) and we can see what it says...
http://www.wolfbane.com/cgi-bin/tvd.exe?MAP=661,936