On the other hand. GPs and hospitals are full of people that don't need to be there and it makes the service worse and reduces the time available for people that do need to be there.
There is a balance between using the service to catch things before they get worse, not using it until it's too late and using it too much. It is admittedly very difficult to know which time is which but our bodies are very good at detecting changes and you have to listen to that and react. Men are much more likely to leave things until it's too late though. Women are much more proactive with their health. The well man checks are a good thing to do because then you are only using GP time if there is an indication that you need to.
The well man checks check overall health but if there's anything abnormal with your heart, blood pressure, cholesterol etc it will indicate that there is something that can/should be looked into further. They don't do in-depth testing though so it doesn't catch everything. Really they are just going to let you know that you are overweight and at risk of x, y and z which if you are overweight you probably already know. I'm not old enough to have one but we have had them through work and the advice to everyone was pretty much the same (do more exercise, eat less, stop smoking, stop drinking etc). If there is anything abnormal, especially where there is a family history, they'll refer you to your GP for more in-depth investigations.
The most important thing to realise is that a "Full MOT" is not a full MOT. There are a million things that could still be missed. You don't get a full body MRI, CT or X-Ray unless they find something elsewhere so you aren't getting much more than you'd get with the free NHS check. You aren't getting full blood work, just a specific panel for common issues. This sort of thing for £1k is really just something those companies offer so they have something to show for being something you pay for. It's just unnecessary upselling. I think if you are the sort of person who has health anxiety and is willing to pay £1k for peace of mind then it is not going to give you that peace of mind for very long and you'll be paying £1k every year. The same as your car, how many cars break down because of something not caught on the MOT? Most MOT issues can be avoided if people maintained their vehicle properly and health is the same.