email received from iSupply 13/4/18:
Thank you for your query and I apologise for the delay in responding. With regards to your questions;
 We offer E7 tariffs for E10 meters
 Currently iSupplyEnergy does not do meter installations.
 We are unable to support the more complex 3-rate and 2-MPAN (related) meters.
If you have any further questions please do not hesitate to contact me.
Sales Support Coordinator