I did the same, a quick trip to Rutland water and a decent bakery on the way home. Downside the car was covered in sh--t when I got home, so a second clean in a week. I've found, topless the heater on one, and the control about an inch up from the bottom, gets me toasty in 10 minutes, almost too hot at times. With the top on, I had to have the windows open, again get too hot.
What I did not know was just how dirty sports cars get being so low. Got some E5 this week, and a big Audi pulled up beside me, the woman looked out of her window, and her head was above my roof. Seriously guys, given that farms and very rural drivers many need such big vehicles, but really,
do town people think it's ok? I know each to their own?
I had the car detailed from new, and it really does help with cleaning in times like this. Just a quick wash with soft soap, and a extra large micro-towel, and its done, wheels take longer however?