I encountered the new Grid Serve chargers at Potters Bar Services on M25 with Double-headed CCS but because one was in use the other wouldn't connect. I spoke to customer service who said that they'd rolled out the upgrading of the Ecotricity Rapid chargers on the site to Ultra Chargers, but the upgrade of the higher capacity cabling infrastructure to the chargers require a lot of additional work so they'd limited each charger to single connector delivery per charger. As soon as the first connected vehicle finished their charge, I was able to charge.