I've never bothered with it myself and never activated it, but AIUI, the free version is SD format while, special sign up offers aside, you normally have to pay for the HD version.
Your £3 sentence seems to imply that part of the deal you got when you signed up was free HD until August. Unless they have it totally screwed, as screwing things up and getting them wrong is one thing they excel at.
I used to get 4 to 6 weekly reminders about what I was supposedly missing by not activating my free TV service until I got fed up with them and told them to stop spamming me.
Edited by jcym (Sat 21-Jun-14 16:45:28)