You're split for choice then
Whatever monitor you buy, I'd suggest getting one with Freesync / Adaptive Sync. Which will let you play without tearing / reduced stutter as long as framerate stays within a certain range. It generally doesn't add anything to the price tag of a monitor so is a no-brainer these days
One of the best options in the 'budget' category - i.e. a 24" monitor around £120 - is the AOC g2460vq6. What makes it stand out is its freesync range (the framerate range at which freesync operates) is extremely wide - 35-76hz.
However, that's already £120 for a ~75hz monitor. Going to £190-200 easily nets you a 144hz monitor. You can see options here:
The AOC 24G2U is relatively new and quite popular, being an IPS panel with 144hz and freesync. There are TN panels too if you want the fastest response time possible e.g. AOC G2590FX, AOC G2460PF, HP 24x, and many more.
Note that some popular but older models don't have freesync, like the
BenQ ZOWIE XL2411P, and the Asus VG248QE I believe, so I'd avoid those personally.