Simon:
I also have a removable wheel, and I agree with Malcolm on the wheel position as that is where I positioned mine.
I can tell you that the back of the steering wheel is approx 7 1/2" from the pointed part of the dash where switches mount. I am 5' 9" and for me that is a good fit. As far as wheel height my column is very close to the top point on the cutaway below the tach and there is plenty of room for my legs, and entry and exit from the car. My column is rather simple, a 1 1/2" aluminum tube with bearings at both ends, and a tubular cover where the column passes thru the dash, so the center would be 1" below the cutaway in the dash, I am using a 13" diam. wheel.
Cheers
Phil