The advice others have given is spot on. The only thing I would add is that if you have never used a public charger before, then go try using one near where you live before you go on a long journey so you have had some practice first, and know what to expect.
When you plan a long journey, give yourself several options along the way just in case chargers are in use/broken when you arrive. Zapmap is good for seeing if there are porblems with chargers along your route. ABRP (A Better Route Planner) is also useful for planning charge stops on long journeys.
Companies such as Costa, McDs, KFC, etc often have chargers in their car parks as it potentially will drive up sales for them. However, the supermarkets are also beginning to deploy rapid chargers. Sainburys is currently on a massive rollout UK wide, and their chargers only work via contactless, but are quick and easy to use. They use Kempower chargers (same as Osprey) which I personally like.