ace,

Airline? Flight number? Dates of travel?

Darren

Ace , I'm assuming you are flying BA , flight no. BA0133 , they now seem to be using a four class 777- 200ER , it used to be a three class 767 , the changeover of aircraft only started from April 1st .
Seat plans are on http://www.ba.com Or you can find more info on http://www.thebasource.com. This even tells you the plane registrations that have made the flights on their BA Tracker tab as on some 4 class layouts there are a slightly different number of seats in the F cabin, the WT+ cabin and in WT or Y cabin it only varies by a seat or two though , nice plane considering just over a 6 hour flight .

I am flying to Jeddah from Heathrow on teh 14th July 2014 returning 29th July 2014. BA0133 British Airways

Ace , it's the plane I have described as above , on checking those dates it appears that seats in First are available to purchase which means that it is a 4 class plane

LHR-JED is operated by B777-200 configuration 17F - 48J - 24W - 127Y hope this helps.