you can go to majorca whenever you want but you'll need your valid passport to get back into the uk. so as long as you're coming back before your passport expires, you're fine. :-)
You're probably OK going anywhere in the EU until the date of expiry, and possibly even returning after it has expired; but there are many countries - eg Indonesia and most Latin American countries - which require at least 6 months validity on your passport.
I travelled to Madrid (and back) with a UK passport 3 months out of date. I was told by immigration that EU countries normally allow you entry if you have a British passport that is not more than 12 months out of date! Not a lot of people know that! This was before 9/11 though - things may have changed.
I agree - make sure you check with the embassy and tour operator. My passport needed to be vaild for a further 6 months after its expiration date when I went to America.
If you renew beforehand, they will credit you with the time remaining - I renewed mine last Oct altho' it didn't expire until Feb. My new one expires Feb 2014.