The 7kW Tesco chargers are usually free, the idea being that you just top up the battery a bit whilst shopping.
There are also rapid chargers springing up at Tesco which do charge a fee, 24p per kw/h at Crawley Tesco
These chargers at Tesco are on the Pod Point network
https://pod-point.com/rollout/tesco-ev-charging
Plugshare can show you where most of the chargers are, how much they cost, etc.