I have one survivor from 4 I rehomed, they soon settled down and although they get rid of them at 18 months because their rate of laying goes down, nobody told them and they continued to lay, I still have one left 3 and a half years later and she still lays an egg most days. She does have a cock for company so isn't lonely
One of them died nearly 2 years after rescue, another about 2 and a half years after rescue and another 3 years later.
5 years old is old for a rescue, but non rescues can live 11 years, so very sad, it takes it out of them laying every day, they need a lot of good food.
They are so friendly to people, and they all have their own characters.
Best not to put jumpers on them as when the feathers start coming through they catch on the jumpers and that's painful for them.
Yes you do need to register with defra but it only takes a few minutes so not a big deal
Rats are there before you bring chickens into the garden, that I know for sure, next doors cats used to catch them before I had hens, and I would occasionally find a nest in the compost heap, they come up from the stream nearby and from the railway embankment nearby. You just become more aware of them as they eat the feed. So lots of mesh and stones and bricks etc if ever you see a hole or see signs of them. My old hens did get killed by a fox, I've tightened up on security now and the foxes now just snack on bunny rabbits in the fields down the road.