Arnott seems to be the aftermarket standard. I bought "OEM" air struts from LRdirect and they came in Britpart boxes. I think Dunlop is OEM supplier.
The LRDirect supplied ones were a joy to have installed. I noticed the front end felt a ton better. My part number was RNB501580G.TR. Which is BWI. I think the shipping from England has become more reasonable these days. Also I would check advanced factors as well. If you need lower control arms, do those at the same time. Also replace the tie rods while there.
Some tips:
- Get new hardware. The lower bolts can seize and die. Also if you accidentally lose a top nut, its gone...forever... Have spares.
- Trim a piece of the air hose off, like 1/8" or so. You can see where the air fitting on the strut "dug in" into the hose. By trimming, you offer a new piece of pipe for the new air fitting to dig into.