Hey folks, thought I'd just chime in with my experiences as well, though a few aren't particularly recent:
Vogel Motors in the Hutt - had pretty good experiences with them when I used them, always helpful and after an owner change in about 2019 I think, they were still good to deal with (probably last time I used them was about 2020?). My parents are out in the Hutt though, and if they needed a mechanic I'd most probably send them there I'd say. Also they used to have a Gearbox Specialist called Ben - I think he ended up leaving, but awesome guy and did some awesome (non-gearbox) work on my car!
Hutt City European - again reasonably good experiences with them. My car previously had an issue with not being able to plug a scanner into, and then conveniently developed an Airbag light which needed rectifying. First time round they did this pretty well and got the code and all was well, the next time (again about 2019/2020 perhaps?) they'd had some staff move on, and this time it was an ABS Light. The tech did manage to get the two codes from the unit, but couldn't figure out one of them (one was a wheel speed sensor, the other was the unit not turning on). I eventually solved all the issues myself (including the non-diagnosis ability), and the ABS unit turned out to be a faulty relay, where it made a click but didn't connect one of the two output poles, so it seems they didn't check the relay function, which didn't leave me super impressed given the time and money factor. Still, hear very good things about the shop and the owner and a couple of the higher up techs are definitely car-nerds, which is always a good sign. Plus, when I was there they were working on my car, a Saab, an Alfa, a Ferrari 355, a Maserati Granturismo, a Porsche Cayenne (Fuel Pump) and something else I can't remember, so they've got experience with a lot of brands (and quirks).
Jon at Auto38 - Easily the best BMW Mechanic in the region (well used to be) - knowledgeable, friendly, helpful, and also was passionate about the cars, so knew all the random stuff you find by owning these cars and scouring the internet for the strange things they do. A shame he shut up shop (but understandable)!
Wellington European - I went there for a warrant, and there were loads of nice older/newer cars, but I found they were quite rude and condescending to me - a very strong "Your kind isn't really welcome here" vibe as I've got an E36 (one of the cleaner examples on the road), and they seemed like the kind of shop that was about money/status/flaunting etc, rather than car-passionate. With that said, a wide mix of Euro vehicles when I was there, including an Isetta.
Auto Tech Miramar - not a BMW Specialist (or even Euro Specialist), I just happened to go there for a warrant. The owner seemed pretty nice and to care about the quality of work, however I was charged both labour for the warrant and a warrant fee, so was close to a $180 Warrant (with no mechanical work required). Heard from others that they were happy with his work working on their non-euro cars.
Sutherland Performance - Again only experience was a warrant, but seemed to be a pretty good shop full of car-passionate folks, and quite a mix of cars/things in there - when I was in, there was an E90 getting some subframe bushes done from memory, a Civic Type-R (current generation) getting an exhaust and a tune, a Saab getting Saab stuff done to it, as well as the usual Golf Suspension work etc. So clearly got some experience with Euros and with a variety of stuff, my only thought was the labour rate is $150/hr, so if any tasks blow past the estimate, that has the potential to stack up pretty quickly. Was thinking I would go there again for a warrant, but might check out All European Service looking further up the thread.
Hopefully this is helpful to someone!
Edit: Managed to get a Warrant by Peter @ All European Service - was just a WOF in the end as I sorted out some driveshaft stuff myself, but my experience was he seemed like a decent & reasonable guy (practical as well) - so can recommend him I'll likely be going there for my next warrant again I'd say.