Last week I phoned Sky about an error in my online bill and they asked if I wanted to take up the offer. I was offered and accepted Broadband Unlimited free for 6 months and then cancel Unlimited before the 6 months is up and go back to Broadband Mid (or is it now called Everyday?).
I was told that as an existing customer who was no longer tied into a contract I was able to cancel after the free 6 months and revert back to my normal Broadband Mid at £5 per month.
As expected the upgrade has made no difference to my download speeds, I can only get around 3.5Mbps, but my upload speed has increased and of course there is no monthly download limit.