I believe all SMETS2 UK smart meters do use Zigbee and probably the majority of SMETS1. This is the protocol most IHD - In Home Displays use to talk to the meters.
See - https://www.geotogether.com/blog/choose-basic-consumer-access-device-can-smart-connected-system/
There are some bridges aka Smart Meter CAD devices which use Zigbee to talk to the meters and then bridge the data to your LAN or they might alternative upload the data to a cloud service which you could then in theory access via a smartapp in smartthings.
(Smart Meter CAD = Consumer Access Device)
Ovo Energy used to give one away but have stopped. 
However look at these.
https://rainforestautomation.com/rfa-z114-eagle-200-2/
https://presciense.com/gateways/mira
https://www.hildebrand.co.uk/our-products/hub/
(I am sure there are others as well.)
There is also an automatic energy switching provider called TheLabrador which provides a free monitoring device callled the Retriever which sends your meter readings to their website. See - https://kb.thelabrador.co.uk/troubleshooting/how-do-i-install-the-labrador-retriever-device this is also a Smart Meter CAD.
One of these should be possible to create a Smartthings DHT and/or Smartapp for.
See https://rainforestautomation.com/support/developer/ for information about their API. This seems to be a US originated product so we need to know if it is usable in the UK. The first step would be working out how to pair it. TheLabrador Retriever is specifically for the UK and they obviously know how to pair it with UK smart meters. Interestingly it is very similar but not identical in appearance to the RainForest Eagle-200.
UPDATE: Seems some people (presumably Americans) have successfully managed to link the RainForest Eagle-200 to Smartthings. See - SmartThings and Eagle by Rainforest (Energy Monitoring) Connection?
UPDATE: The Eagle-200 being US originated may only support US radio frequency for Zigbee. I can see they do sell to Australia as well which uses the same frequency as the US. 784 MHz in China, 868 MHz in Europe and 915 MHz in the USA and Australia