I got a used business dell a couple of years ago for £300. It still had active service warranty which dell transferred over to me. I upgraded the ram to 32gb and the ssd to 1tb and it was pretty decent for the time - i7 10th gen from memory (without grabbing the thing to check).
It’s a latitude 7390. I was mistaken, it’s an 8th gen i7, but still pretty new at the time I bought it. Bonus - Dell put all their service manuals online so you can always find instructions on how to tear down and upgrade