Tesco store finder helps Ron, if they stock Momentum it should come up in the listing once you choose the Store, it's also usually much cheaper than Shell.
https://www.tesco.com/store-locator/uk/
eg
https://www.tesco.com/store-locator/uk/?bid=5441
Notice that particular branch has a defibrilator too, handy for those filling S8s when they get the bill
