Gill Charlton (the Daily Telegraph travel guru), recently gave her advice on passport validity, post planned return date.
For what it is worth, her advice was to make sure that you have at least 6 months (passport validity from your planned date of return) for all destinations, other than within the European Union.
Within the EU, your EU passport is valid until its date of expiry.
If you are travelling outside the EU, make sure you meet all the immigration requirements for your chosen destination (and any in transit – if required).
Gill was responding to someone who was refused entry to South Africa because they did not have a full (un-stamped) page within their passport – to take the visa (to be placed in their passport on entry).
Best be aware of any esoteric requirements that could ruin your holiday plans.