Let's begin by stating the fact that the G-Sync you apparently had hopes for will usually bring a cost premium of £200 or more. Meaning that if we have a monitor with a price tag of £300, then an otherwise identical monitor with G-Sync support will cost £500+.
Also, if you look at OcUK's
G-Sync collection, you'll quickly notice that the cheapest G-Sync monitor is £360 (Acer Predator XB241H), and its still a TN panel. So, unless you're willing to almost quadruple your budget, just to get the worst G-Sync available, then you have no chance of getting a G-Sync. So I'd simply forget about it, for now. If you still want variable refresh rate functionality, then you'd be better off looking at FreeSync, the premium-free alternative for G-Sync. It's also more ubiquitous, mostly because it is (like the name suggest) practically free for manufacturers to implement it in their monitors.
But don't get your hopes up, just yet. If you have an nVidia GPU, then you can't take benefit of the FreeSync feature (although the monitor otherwise works like a normal monitor). Same goes for an AMD GPU with a G-Sync monitor, btw. At least for now. The FreeSync keeps getting more and more ubiquitous, so nVidia will probably at some point have to start supporting FreeSync (or rather the Adaptive-Sync, in which the FreeSync is based on). Either the support will come in their GPUs, or in their G-Sync chips on the monitors, or both. The reverse, meaning G-Sync being supported by AMD GPUs or FreeSync monitors, probably won't ever happen, though. AMD certainly wouldn't mind supporting it, but nVidia is probably not that keen to open up its G-Sync IP. And FreeSync monitors can't support G-Sync, as G-Sync requires its own scaler chip.
Anyway, let's state the second fact: with £100, you're quite simply looking at the bottom of the barrel, just like andy_mk3 stated earlier. Let me be more blunt: don't expect anything good. Now, while
there ARE cheap FreeSync monitors (there is even one with £100), the cheaper ones usually have some drawbacks. But, if you REALLY want to keep the budget low, then take a look at the
LG 24MP59G (£140).
For 144Hz and VA panel, take a look at these:
Samsung C24FG70 (£300)
Acer XZ271 (£360)
Acer XZ321 (£400 on sale, atm)
I have the last one (XZ321), and I'm very happy with it. But for most people, 32" is too big (or rather, the desk size and/or resolution is too small). Also, considering you started with the £100 budget, the
LG 24MP59G at £140 might be less of a shock to compromise to. It is 24", 75Hz and IPS, so it should be fairly OK. The build quality on the andy_mk3's suggested Samsung is probably better, and it is also cheaper, but FreeSync and IPS far overweigh the TN.
