I've got the Coleman Evolva Link annexe - it's quick to put up and doesn't occupy much more ground space than the unit itself.
It's 2m square, and as you see, opens on three sides, but can be totally closed.
Built in ground sheet as well, so it keeps most water out.
Zips up on either end, to the Evolva Sleep Annexe as well, so you can upgrade it to take the missus on a camping holiday as well! Sleep Annex is a double-skin two-berth unit with vents, screen, etc. Proper tent.
With two sleep annexes, it looks like this:
(That's my reason for choosing this as the "family" tent - a third of it goes racing!)
PS. Strange, but it doesn't come with poles to raise the door into a canopy, but £8 solves that...