Which Groupset?

Strongly suggest rival. You’ll get a warranty and something up to date. The 11 speed FD is out of production I think now and chancers sell them at an inflated price on eBay, so if it ever breaks you’re up shit creek.

The performance of rival is brilliant, I run it on my gravel bike and it’s faultless.
It’s pretty hard to justify red or even force axs for anything other than bling points really.

11 speed Red Etap or mechanical? Hydraulic brakes or mech? What's the bike?

just the response i needed to persuade me to spend...

and it was axs rival vs red hyrdo 11-speed etap (second hand)

You won’t regret it. I bought all my rival axs bits from r2-bike.com
Worth comparing prices with them before pulling the trigger, it worked out cheaper for me even with import fees.

If you don’t want to change freehub you could even use 12 speed shimano 105 cassette, chain and rings.

Sunrace 11-42T, £56
11-13-15-17-19-21-24-28-32-36-42
https://www.ebay.co.uk/itm/334696528576

Shimano M5100, £40 if you buy two
11-13-15-17-19-21-24-28-32-37-42T
https://www.ebay.co.uk/itm/334771968109

Anyone ridden both for comparison?

Corratec casually put unreleased mechanical 12 spd 105 on a display bike at Eurobike

https://youtu.be/6j9TnzTcR8g

Lol

Has anyone here used force d2?

Not really but shouldn't be any different functionally than d1

Sram is releasing Apex AXS 12 spees and it seems basically identical to Rival apart from surface finishes?
Why pay more than Apex AXS? Just slight weight improvements and nicer brake bleed ports of the roval, force, red. Could be wrong though.

If you want best weight/bang for buck, buy - Apex shifters and derailleurs, with Force cassette and chain, with a Red chainset. Change my mind >>>

Yeah, sounds perfect.
Although the Red chainsets seem to be ridiculous money don't they

Do I want a 1x12 groupset?

Let me elaborate.
A few weeks back I rode a loaner Fairlight Holt with an XT M8100 1x12 groupset. I gotta say, at 34 to 10-51, I loved the range. I also loved how well it shifted even when I got it all caked up. The main use for this bike is offroad bike-packing and some fun gravel and single trail riding.
Atm I am running a 1x10 Deore groupset at 34 to 11-42 on my hardtail. For some steeper stuff around here and upcoming trips, I'd like that extra bit of climbing range. I was already really happy with the quality of that Deore groupset. Especially at the low price.
The XT upgrade kit is very reasonably priced in my opinion so it's not a question of budget. My main concern is I just feel like 12-speed components are still very sparse and expensive. I was on a ride with friends the other day and somebody killed their rear mech. We had to single-speed the bike and needed a spare chainlink. There were so many 10 and 11-speed spare chainlinks in our group. Nothing 12 speed though. I also looked up the bits of the upgrade kit separately and the chain is 56 euros on its own. I also like how all my geared bikes are on Shimano HG freehubs. So potentially I can move stuff around. The XT M8100 would require a micro spline freehub. Am I too retro grouchy here? Unnecessarily worrying about non-existent issues?

Merlin has a load of M8100 heavily discounted this weekend
https://www.merlincycles.com/shimano-xt-m8100-12-speed-chain-with-quick-link-171576.html

Cheers! That chain is indeed super cheap but I am not the UK anymore. The initial purchase price isn't an issue. Seems like I can get the upgrade kit (derailleur, shifter, chain + cassette) for about £260. Happy to drop that. I am more worried about the price and availability of spares and I don't like the idea of more and more things in my stable not being compatible with each other.

Everything is 12 speed nowadays in MTB world. It's not even that expensive. SRAM eagle cheaper cassettes work with HG freehub.

even 9 speed can offer that range with Box components

and you dont need microspline to go 12 speed

Thanks, everyone for the input. I believe the sensible middle way for me is to buy an XT - M8100 shifter and derailleur separately, maybe a cheaper (SLX) 12-speed chain and get a SunRace MZ903 11-51 cassette. I miss out on 34 x 10 but save some money and don't need to get a microspline freehub (even more money saved there).

everything 12 speed wears faster

They probably would have a few years ago. Now they're scared of Microshift.

One of the best bits about the shimano 12 speed is the shifting, especially under load, which is due to the HG+ cassette and chain, so get microspline.

Was about to say the same, even in 11 speed I always install Shimano, shifting it's a lot better

I've never been too convinced with the 11 speed, but the first time I rode my HG+ shit I was very convinced it was great, I've not tested different chains but the cassette at the very least works wonders.

Might as well get a cheaper derailleur. There's very little in it apart from the plates. I run deore derailleur and xt shifter.

I've got SLX everything, but the XT shifter is noticeably nicer and deore is noticeably worse.