Although there aren't absolute descriptions, during the story Dan is described, sort of. I've added a couple of bits below.

Hair neither black nor brown, his skin tone quite pale. His profile, though still chiselled, was softer than she’d remembered, sleep blurring the edges. Dark stubble sprouted across his cheek, heavier than the night before.

A dark, fine knit sweater over an open necked white shirt, dark hair, pale skin and brilliant blue eyes.  He was good looking, just as she'd remembered, lean and pale with just and edge of louche. 

I seem to have been a bit remiss with regards to Louise. She is described as being only slightly shorter than him in heels, so that makes her about 5" 6' in bare feet and Dan about 5" 10'. I'm pretty sure I've mentioned she's blonde, longish hair. Attractive, I'm sure that's mentioned, though not directly, more in his reactions to her.

Anyway, I hope that helps! Thanks for taking the time to comment.