>I'm writing this on a 2011 MBP which is running Monterey because of OpenCore Patcher, and it's a bit slow, but everything about it physically is better than most laptops I would get for under £500. This with a faster processor, graphics and RAM would do me for another 5 years for 'general' duties.

I just replaced a 2012 with a 2021 M1. Yes, it's faster. Not having to use a pad to shield my lap from the computer's heat is nice. But I would have continued to use the 2012 had the hinge not loosened to the point where the screen would not stay upright. My computer environment is almost unchanged; Monterey with OpenCore Legacy Patcher to Monterey, 16GB RAM to 16GB, 1TB SSD to 1TB, 15" to 14". The battery life is much better,^1 but I don't take the computer out of the home so it doesn't make a difference in practice.

^1 But not as good as I'd expected. I don't do anything heavy on the computer—browser, Excel, and ssh—and the M1's battery only lasts for about six hours. Can using Chrome as the browser and not Safari make that much of a difference?