I have just found the thread and also went on the Foreign and Commonwealth website. We go on Weds so was in panic mode! It appears that it is ok just to be valid for the duration of your stay and no more.
There is exactly 3 months to the day left on mine. The woman in the post office told me that I had to check as that might not be enough. I can confirm as above, after checking the Foreigh and Commonwealth website and calling them up, as long as you have 1 day left on your passport, you will be ok for BG
Funny really. Apart from skiers boarders and business owners who from the uk is going to want to overstay in Bulgaria. The average wage is £50 per week.