I am afraid you will have to think long and hard about this.
The following info is taken from and thanks go to
www.e34bmwm5.com
Here`s where it hurts.
Production numbers of E34 ///M5 3.6
1988 331, 1989 2339, 1990 3022, 1991 2033, 1992 224, 1993 130
Total 8079 - No good to you, you want a 3.8
Production numbers of E34 ///M5 3.8
1991 120, 1992 1553, 1993 643, 1994 483, 1995 215
Total 3014
So, 3014 3.8 cars built worldwide.
Add the 891 3.8 Tourings, gives a total number of E34 ///M5's at 12249. (There were 265 CKD assembled outside Germany)
YOUR DREAM CAR
According to BMW, from 1989 untill 1995, only 696 cars were sold officially to the UK. This means all of them, 3.6 & 3.8.
That`s just 110 per year.
Now, 696 as a percentage of 12249 means that an average of only 5.68% of cars built came to the UK.
Assuming the percentage imported of total build was the same year on year, and you want a late model, we need to take the 1994 483 count and the 1995 215 count = 698 cars built.
Of which probably 5.68% came to UK = 40 cars to choose from.
So, 40 cars.
From these 40 cars, you have to add on any grey imports, then (tearfully) subtract the estimated number of accident writeoffs or scrapped cars.
Then you have to wait until one comes up for sale.
Oh, and what colour did you want???

LOL
Now this is doom and gloom, but every cloud has a silver lining.

and yours has more than one.
1.
Munich Legends are probably the people I would have gone to if I wanted the best and have the dosh. Them or that famous Norfolk dealer in BiTurbo Alpinas.
I would have another look at that 3.8 in Munich Legends, even though it`s LHD, or make sure they have your phone number and understand that you are a very serious buyer when they get a RHD.
2.
I only have a humble 1990 3.6 with a few extras.
It`s the most amusing, brutal, awe-inspiring thing I have ever had. I can`t believe I actually have it. Just writing this makes me smile. You get to appreciate just what a bunch of muppets are in "The Fast & The Furious".
3.
You have the cash to get a late 3.8 Nurburgring model.
Its faster, more refined and handles better. Its going to be half the age of my car.
4.
Wait. Wait some more. Get the best one you find, and walk away from anything that doesn`t feel right. When you finally get one it will be worth every minute you didn`t have it.
Ivan.
PS. Drive careful. Change your oil. Don`t race big brown things with leaves.