you can checkhere to see if your area is covered, but even if it is, you still might need your aerial adjusted. The only way you'll know is to try it, I'm afraid.
We've just got one (not at that price, though) and think it is probably worth it- not only do you get all-day Cbeebies, but the signal is much better, so the picture is much clearer.
Channels,: BBC1, 2, 3, 4, ITV1, 2, Ch 4, Ch5, Cbeebies, CBBC, BBCNews24 and BBCParliament, ITVNews, Sky News, UKTV history, UKTV Bright Ideas (home improvement type shows), Sky Travel, Ftn (can't remember what that is) a few music channels, and a few shopping channels. You can also get Digital Radio stations.
TBH, we only really watch Cbeebies, and the terrestrial channels, though did watch a Simon Schama repeat on UKTV history last night. The rest are pretty mediocre.