No I don't have a source for that, but if things are to "kick off" this year as seems to be suggested, then sea transport needs to be chartered well in advance. Whilst you can fly troops and light equipment to the region, it is incredibly expensive to fly heavy armour and other big ground equipment and that is if it can fit in the aircraft. The RAF only have four C-17 transport aircraft and the Hercules fleet is not big enough. I do not know for sure, but I guess a ship must take a good 6 weeks to get to the Gulf. In addition the ship has to be chartered and prepositioned in probably either the UK or Germany for loading, so all in all there is a lot of pre-planning involved in the logistics side of a big military operation.