There are not that many 25kg+ ERF seats so not too many to choose from, which makes it (a bit??) easier. These are what I'd look at at the moment:
The Britax Max Way Plus is discontinued so very little stock of it about - I think Little Peas still has a few. £220 so the only "budget" option left at the moment. If I was getting one I think this is what I'd get, however some people say it's a slightly more finicky fit.
Axkid Move is £280 now, which I think is quite a lot for a stripped-down/basic seat. (Still just as safe but lacks some of the comfort features). It sometimes goes on offer, so if you have time you could keep an eye out for this.
You also sometimes get offers on the Axkid Minikid 2 which is about £370. When that goes down to under £300 it's a good option. It's currently full price. (Axkid are consistent about their sales for all retailers.)
Besafe izi Plus X1 is reduced to £270 in a few places which is a good price. However, recommend getting this fitted in person if possible as it's a bulky seat. It does have the advantage unlike many other ERF 25kg seats that you can change the recline without reinstalling it. It's a little bit shorter in the shell than the Axkids, but not problematically short.
Joie i-Prodigi is worth a look if you want an isofix seat, it is a bit more expensive though at £450 (but not as much as the Axkid One2!) People never really seem to recommend this over the Axkid One, so I don't know if there's something not so good about it - it's so much cheaper, it seems like a no-brainer to me - might be worth looking at some reviews.
The rest, which I think are probably not worth spending the extra on for you at the moment (but including for completeness, in case you want to look them up)
Britax Multi-Tech 3
Avionaut Sky
Besafe Stretch
Axkid Minikid 3 / 4
Britax Max Safe Pro
Klippan Century / Opti 129
Axkid One2