Chromebooks stop receiving updates a few years after they are released ( usually 3yrs) So be careful which one you get. It's going to brick itself much like a phone ( it won't... but with no updates and a locked firmware.... Would you really use it?)
Lenovo ThinkPad's are good ; the T460p is a fair workhorse and is a 14" screen, if you want a smaller and more portable, then look at the x270. Either of these can be had for £300 or less with an i7 CPU/16gb ram and 256gb SSD . Avoid the touch screen options. All corporate ones would have sold with 3+ years of warranty, some will even have had 5. So shop around, you should be able to get a reasonable device that still has warranty for a year or so. Avoid all ThinkPad's from 2018+.
HP EliteBook are another good option, that were built exactly into the ThinkPad market. Avoid all EliteBook from 2017+
Or you could just buy the Lenovo IdeaPad 5 15" with the AMD ryzen 4800u CPU and 16gb of ram, brand new for £500 - it runs faster, cooler and longer than the £2500 macbooks and almost all the latest intel 10th gen i7 based laptops. Lenovo is out of stock all over Europe at the moment though, so it might be a few weeks before they start taking orders.
Most phones these days are pretty capable. Maybe just get a keyboard + mouse and a hdmi out for your phone?