I did a quick speed test of the connection via speedtest.net, just to see what I was getting. I've never seen any download speeds in excess of 2Mbps with BT, usually it was in the 1.7-1.9 range, yesterday it was a measly 700kbps or so. Here I am with a considerable speed improvement, which exceeds the expected 5.5Mbps.
So I'm quite pleased, I'm with a Phorm-free ISP, with no contract tie-in, other than 1 month, and my download speed has tripled!
One other thing is that the prospect of changing ISP has always daunted me, but it is remarkably easy, if not as quick as one might expect - MAC requested Sunday 28th September, MAC received Wednesday 1st October, order placed 2nd October - processed quickly with a start date of today. This website has details, specifically aimedat advising customers on leaving BT (in response to Phorm).