Chebby -thanks for your comments also - I was writing my response to the previous comments as you were posting yours!
I only quite recently had a full aeriel instal but wasn't very happy with the job done - the freeview reception was very poor in some rooms and I had to get another installer in to check it out. They installed a couple of new sockets which seemed to help for a while but the freeview reception from one room is now poor again - even though the aeriel has a line of sight to the transmitter only a few miles away.
The FM aeriel for my MF Unit is actually plugged into the TV wall socket as it gets far better reception from this than the one marked FM. I've yet to try a TV in this room so don't know if this will work in the FM socket.
I think I may need to get an installer out to do a thorough check - as it happens the organisation whose website you refer to is in my home City (Sheffield) so I may even try them - they certainly seem to know what they're talking about and are keen to supply quality products.