Welcome!
By far the cheapest way to charge is to do so at home on the driveway. You're doing it right by installing a home charger. There are a number of providers which have cheap overnight rates; EON, Edf, Octopus are commonly chosen due to their very cheap rates.
The normal price for power at home is around 28p per kilowatt hour, these three all have rates below 10p. In most cases, you'll also get cheap power for the house as well during that time - so if you are willing to run the dishwasher, washing machine, and charge phones/laptops etc during the cheap rates, doing those things gets cheaper too.
For charging when you're out and about, I'm sad to say the answer is "it depends a bit". The best starting point for price is the Tesla Superchargers; some of these are open to users of all EVs (while others are for Tesla vehicles only). They cost around 40-50p/kWh. However, there's also Ionity, who offer a cheaper rate of 44p/kWh for a monthly subscription of circa ÂŁ8.99.
You will notice that even 'cheap' at 40p is a load more than the 7p/kWh rate for charging at home: so I'd treat public charging the way you might have treated filling up at the motorway service station: put in just enough to get back home.