Shutter speed is 1/200th. highest speed on that shutter is 1/400th. FP3000B has a nice fast dev time of 20sec for 20-23degrees, which is what it was today. But I do take on board what you're saying (which I think is, let the film warm up to room temp before shooting?)

I'm fairly sure that I did try one with ambient exposure, to no avail, but will have another go tomorrow. Light meter! stone the crows, why didn't I think of that? I do have an ancient Minolta Autometer knocking around. Facepalm!