cool is this the right one? http://www.ebay.co.uk/itm/1-4-UNC-T...466267?hash=item257e85785b:g:p6MAAOxyYANTbMCR
That looks to be the one. Wikipedia has this to say about tripods; so if that's correct, you have it.
Its also the same diameter and thread pitch as the common American size 1/4 UNC. The only difference is the angle of the thread (engineer mode engaged), 1/4 BSW (British Standard Whitworth) has a 55 degree angle whilst UNC has a 60 degree angle. For just about every conceivable application they are the same.
The inner Engineer is strong in this one! Nice info, been using tripods for decades and never knew that