As a Brit, living in a standard 'semi', I can only drool. I guess I am luckier than most to have the use of the spare double bedroom, but haven't had the courage to jettison the bed yet!!
Having extended the ground floor here, I agree with the mantra of 'plan, plan and keep planning'. I can remember getting out of bed in the middle of the night with a new thought in my head and a tape measure in my hand.