http://www.nebula-media.com/ is a good place to start, you pay roughly 70quid for the digitv box and then your sorted, any software updates are free and it comes freeview ready.
the biggest part in my opinion is getting a good quality aerial for a signal
I've not used any other devices for TV personally, but i've had this for about 3 years and been solid from start til now, so i can certainly recommend it.