Thanks both, was pretty convinced I had all zips shut (external door, internal door and flap at top of internal door), wouldn't put it past me to miss a whole extra one though! ... from the other side looking in the door to the internal compartment looks pitch black. May have to do a 2nd test pitch (or just wait until on Worthy Farm!) to make sure I wasn't just being an idiot! Will try to pitch with doors west facing though!