I know this was mentioned previously and was dismissed by some as an unattractive option, but I have been using the Bonnet service for 7 or 8 weeks now and have found it to be pretty good. On pay as you go you only pay 35 pence per kWh on any of the partner network chargers, which is a combination of rapid and fast chargers.
Click here to see the charging network
Bonnet - Partners and if you do decide to sign up for a refill, your price per kWh will fall to as low as 25p per kWh. If you do decide to sign up for a refill and quote my referral code, which is RVXGQ we will both be credited with £15, which means your first months refill could be free.