I'd write a list of must haves, nice to haves, and definitely don't wants.
I did this and then got the information from each coastal area I liked the look of - Swanage, Exmouth, Broadstairs, Worthing, etc. Because I wanted my kids to get to me easily, I eventually decided on Exmouth and Broadstairs as they both have good train links.
I was widowed in 2016 and moved up from Twickenham to Northumberland with my late husband in 1999. I wanted to go home to the south, but didn't have enough money. My budget was £240K and when I visited Exmouth and Broadstairs I could only afford the not so nice areas.
I've stayed in Northumberland and would recommend Alnwick to you. Has a bus station, a small hospital, supermarkets, doctors, dentists and vets and the beach is only a five minute drive to Alnmouth, where the railway station links to London or north to Edinburgh/Glasgow. Many downsizers here head for Alnwick as there is a fear that the country buses that visit villages will eventually be stopped.
Really nice people here with lots going on and Newcastle is a forty minute drive with its museums/restaurants/good shops.