Hi folks,
I am coming back to this topic as in the meantime I have been looking everywhere for alternatives to OEM shocks.
After exhausting almost every other brand out there, I recently came across a company based in the Netherlands, named INTRAX:
https://www.intraxracing.nl/
I exchanged a few emails with Donald Molenaar at INTRAX and they actually do fabricate bespoke shock absorbers/coilovers/springs for BMW cars upon request.
Regarding the M5 - they offer options based on their 1K2 model (which is adjustable in height and damping). They can customise and adjust to your specific needs (street, trackday, race, rally). On top of this they have various add-ons (that you pay extra) like adjustable camber plates, special coatings, anti roll control etc etc.
This kit (without any add-ons) would cost me £3350 including adjustments, fitment, wheel aligning etc at their factory in the Netherlands.
The downside is you have to go there - from where I live it is 310 miles and because I would have to cross the pond it would take me almost 5 hours and 30 minutes. Which in my opinion is very doable.
But the costs would further add up as I would have to consider ferry tickets,tolls, fuel cost and at least 1 night at a nearby hotel plus subsistence etc.
BUT
if you are serious about your suspension setup and wanted to go the extra mile and have it tailored to your spec, then this is the way to go. I can't think about something else.
I wanted to share this for everybody's information as I started the topic and wanted to come up with some suggestions apart from the "standard" KW and Dinan kits.