So I got the tyres mounted today and they make a HUGE difference. The handling is still a bit loose as they aren't near scrubbed in yet but I no longer have to cringe every time I roll over a slight imperfection in the road! It's like advancing 150 years in tyre technology in a day!
Unfortunately my night was kind of ruined as I was coming back from BMW on the motorway and the car in front of me kicked up about half the tread of a semi trailer tire (ironically) which hit the front of the Z4, dislodging the passenger kidney grill and sending it flying onto the shoulder at about 65 mph.
I had to walk back a midst the rush hour traffic to retrieve my grill. Fortunately while it had separated the chrome ring (currently plasti-dipped black) from the outer edge by breaking off the tabs that hold it on - it was otherwise undamaged. The car suffered only rubber scuffs which wiped off and once I straightened out / snapped back together some other bits of the front end it seems almost as good as new. I stopped off for some plastic weld 2-part epoxy and that is currently curing, gluing the ring to the kidney. If all goes well and that holds up I should be able to re-install my grill and be happy again by tomorrow evening.
For now though... there is beer.
Oh! I also ran OVER a very young deer today which was sleeping in the road. I thought it was just general roadkill and the choice was either hit the oncoming car, hit it directly with the tyre or try and straddle it and hope it doesn't hit the underside of the car. I chose to straddle and as I was passing over it (60 mph) I heard a very slight knock as it hit (presumably) the front tyre mudflap that extends toward the center of the car. I heard what can only be described as a baby deer scream (it wasn't dead, turns out...

) and as I looked in the rear view mirror I saw it get up and run off the road like it had... well... just been slapped at 60 mph.
It's been a bad day... collision-wise. Probably also not the best day for that deer.