I opted for a single rate with Igloo. At first they charged(standing) for two meters then rebated and changed it to one charge, I thought this was their generosity until I read this recent post.
I must say they are a breath of fresh air after months of trying to get any sense fron Eon who seemed incapable of comprehending even the simplest query. As said previously their single rate is on average cheaper than most E10 average rates. I am considering an E7 meter but only if the single rate is an option, this may depend on the supplier.