I just signed up to Polar to try it and I believe every new customer gets the 3 months free BUT you are liable as all Polar users are, for charges (at some sites)It's actually from £19.50 per month but still outrageous.
For what it's worth Polar are currently running a prize draw: the prize is a night in a luxury hotel, a home charging unit and 1 year of free access to the Polar Network. Also, every entrant gets 3 months free access to the Polar Network.
I can't enter yet as I'm still waiting to hear when I get my Volt and you have to include your registration number on the entry form. I'm not even sure that I particularly want the 3 months free access to their network when I know there's zero chance that I'd sign up at those rates, but FWIW, http://www.polarnetwork.com/Competition. There is a skill question to answer, but I'd be extremely surprised if anyone reading this forum didn't know the answer. Closing date 28th May 2012.
I may switch to the OVO fixed EV rate which has 2 years of Polar subscriptions included... I was going to go with Ecotricity but my questions about the i3 issue and their CCS problem met with radio silence... which is surely a sign