Housenetwork basically do what estate agents do, except the viewings. i.e, bugger all!
They came round really quickly, did a lot of very good photos. The blurb they wrote was a bit formulaic but you can go online and edit it yourself, which is much better than having to hassle an estate agent to change what they've done.
It goes on RightMove. Viewers phone/email HouseNetwork and HN call you. You show the people round. Then HN call them, get feedback and stick it on your online account so you can see it.
It's an admin service to get the viewers to your house. They don't do any "selling" in terms of encouraging individuals to buy your house. If you have the choice of a good estate agent, (ones who are actually salespeople) then I'd pick them.
All our local estate agents basically act as an admin service to get people to view the house, so for us HN was just as good. Better, actually, cos we haven't had to put up with loads of viewers who weren't really interested in our house but just came cos the EA pressured them!