Sorry, wasn't ignoring you, just had tired couple of days!
I quite understand and we did the same thing. DS2 is also 99th centile for height which is an issue. We got the Joie 360 Spin partly because it was one of the cheaper ones, but partly because the shell is said to be tall and he is already on the 3rd or 4th headrest setting (out of 6) and he is only 17 months. So as long as you're aware you're not likely to get to 4 in it, that's all I'd want someone to know before buying. I haven't decided yet whether after this we'll go forward facing with harness or ERF to 25kg. I did see the Britax Max Way in the flesh and really liked it, but we decided we wanted the spin feature and better recline more, at least for now.
The 18kg ones do take up more space front to back as well which is worth noting, but I can get a click or two more out of the front seat if DS2's seat is upright than I could with his infant seat, so that's better.
As always, best to try seats in your car if you can. Smyths and Halfords tend to have a good selection, you can also try searching Britax or Maxi Cosi's website for stockists as those are the two most popular brands in the UK and most easy to find.
OK so spin seats up to £180 is tricky. If you can hold off until May you might find there are sales again. At the moment, everything seems to be close to RRP, so £200 is more likely.
Cuggl Owl Spin is Nania Revo, which is only RF up to 13kg and has a safety warning on Which? - I am not subscribed so can't read in full, but would not recommend.
Migo/Osann One 360 (And I think the MyBabiie seat is the same one) - I'm unsure about. It is RF to 18kg, and spins. Other Migo seats have been safety tested and do OK, not great, but OK. But Migo (and Osann) are part of TeamTex/Nania who I in general don't trust at all - they have several extremely poorly-performing seats which they have simply withdrawn and then brought out the exact same seat in a new colour and a new name! So it's tricky to keep an eye on what they are doing and I don't think it's very honest or safety-centric. In the product video of this seat as well, it looked unstable. It's only £160/170, and I can't find any outright warnings about it, but those are the only two positives I can see. If you decide to get it I would be cautious about the booster seat mode and check belt fit.
Cosatto All in All - no independent safety reviews, and not spin, but RF to 18kg with isofix for £165. I would say be aware the booster seat mode may not be the best, and seats which encompass all groups generally don't seem to perform as well on safety.
Britax Dualfix 2R is currently on sale at Boots in just one colour but is out of stock (they have a note saying more coming soon) £175.
www.boots.com/baby-child/pushchairs-car-seats/car-seats-accessories/britax-dualfix%C2%B2-r-moonlight-blue-10266896
To be aware of with Dualfix is that the original models were very short in the shell. I would check this, as I don't know if the 2R is one of the original or improved shell versions. If you can find one somewhere to try out. Elsewhere/in other colours, it's £225.
You can get the original Dualfix for £199 on Uber kids, but that definitely has the shorter shell.
Smyths carry some BabyAuto seats. This is a newer brand to the UK market and they mostly trade in Spain. They are a budget make with some seats looking more sturdy than others, but no independent safety tests on them. I would use one - I am likely to get one as a spare for when we visit relatives in Spain. You could look at Infinity Fix which is rear facing up to 18kg, unfortunately not spin though, and needs top tether but it's only £150. Seems they are out of stock in plenty of areas so you might be stuck.
Another BabyAuto one to look at would be BabyAuto Dupla - that's rear facing up to 18kg and also forward facing to 25kg with harness, which is a plus for a tall child. Again, no spin, and it needs top tether (to forward face after 18kg), and you have to seatbelt + isofix it in rear facing mode, which looks a bit annoying. This one is only £140 but isn't in stock yet, you can preorder at Smyths.
There is a Cozy n Safe seat - I don't know much about this brand other than they are a budget make and I think based in China. Merlin - a bit over your budget at £189 but available at Halfords.
Joie 360 spin is usually around this price or under, but currently is £199 everywhere. As it's available at some big retailers, you might be able to find some kind of £X when you spend £Y code. You want to check the fit in your car. It's perfect in ours but in some it has terrible wobble and rattle.
Then you've got seatbelt fitted 0-18kg rear facing seats, all of which are under £180:
Joie Tilt (short in shell)
Joie Steadi
Joie Stages
Joie Every Stage/Verso (does not do great in testing)
Graco Slimfit (possibly suffers from same "all stages" seat problem)
Would also avoid Lionelo and other random, unknown brands you can only find on sites like Amazon, Ebay and so on as these are going even further into the realms of dodgy and some may even be counterfeit/not actually meet standards.
If it doesn't come back into stock or turns out it's much shorter then the Joie atleast is there as a backup.