There are actually very few countries which have a '6 month validity rule'. (Even the USA, which has some of the strictest entry requirements in the world, waive their normal 6 month rule for UK passport holders).
Assuming that you hold a British (or other EU) passport, you'll have no problems entering the Netherlands. EU law requires all EU countries to admit any EU citizen who can prove their citizenship by presenting a valid passport or national identity card. You could turn up at Dutch passport control with only a few seconds validity left on your passport and they'd have to admit you.
However, if you want to renew your passport, any unexpired period of validity on your old passport (up to a maximum of 9 months) is automatically added to the validity of the new one.
Chris