Regarding Gorleston, I love it, but it has a very, very different vibe to North Norfolk, which is why I didn't suggest it. However if you want more bang for your bucks in terms of house size, it's a great idea, funnily enough I was walking on the beach there yesterday and met a whole bunch of Londoners who had come up for the weekend and were considering it as a retirement option!!!
It's true by the way that if hospital access is important to you, then Norfolk has a limited choice. However, Cromer hospital is expanding, they now have a Cancer Unit ( before everyone had to go to Norwich) and I had a medical procedure there during lockdown ( Norwich had a covid outbreak and closed wards) and the care was excellent.
Also, I missed that you don't have a car. If you don't North Norfolk will be difficult for you and your family, especially in the winter...public transport sucks here, Cromer would be your best option but even then you might find it very restrictive.
Much as I love Overstrand, it's really more of a lovely retirement village, and I don't think it should go on your list, there's a village shop, and a pub, and a garden centre, used to be a little art gallery, but not a lot else.
I still think you should come to Norfolk by the way, one of my closest friends moved here from South Woodford in her early twenties and she is still here, but moved to a small village on the Norfolk coast to start with ( Kelling) and it was very hard going for her and her family. She's now been in Norwich itself for thirty years and absolutely loves it!