looks pretty good. i have a garage and currently have half a ford puma in it. unsure whether the z4 will go in with enough space to get out 1 side though. did you measure the narrowest point?
Ben G - standard garage width so all good. Super high at back end (18ft) which enabled the mezzanine. Driven in there's about a 1.5 foot gap each side but I tend to park to the left so I have a wider route to the ladder and under the upstairs. Also bought a cheap camping roll mat and no more nailed it to the wall so door doesnt hit brickwork when getting in/out.
Pic below shows it with car in situ (ignore the frost on the car!)
Stuart - It has been suggested. Would be warm enough in sleeping bag so the option is always there.
Spearman - Thanks man. Nowhere near the spec you're working too which looks amazing. Garage has seen 2 x Zeds. First was my old 3.0 roadster sold to fellow forumite last July. MC lives there now in the spec up initiative.