http://www.bigpockets.co.uk/product....duct=GRADEA315
I use one of these - sadly now out of stock - can't be bad for ?12.48 delivered! But you may find elsewhere.
It seems neither more nor less sensitive than my set-top boxes. The little stick ae provided does not work now, but may well do so after changeover with vastly stronger signals.
I wonder if the sockets in your rooms might be for VHF radio? Do they get analogue TV?