OAG's definitely have an advantage over individual airline timetables because the frequency of timetables is varied and unreliable. Some airlines don't print them anymore. Some airlines are very religious about it (like every month no matter what) but other airlines are not -- if you find a June 15 2002 timetable and an October 1 timetable, you don't know if the 6/15/02 timetable was accurate through 9/30/02 or if there were intermediate versions. And it's not uncommon for airlines to make changes which are not coordinated with their timetables. Perhaps that 6/15/02 timetable went to press on 6/1/02. The airline could easily make adjustments to their flight schedule after 6/1 which affect things later in summer or early fall -- maybe they decide to reduce a seasonal frequency as of 8/31 instead of waiting until 9/30...and it would never show up in a timetable. Finally, you might miss some airlines by not knowing they flew to LGW for a time. The OAG shows virtually everybody, including some who don't sell in normal global distriburtion platforms. Being a US guy I'm not 100% certain about the scheduled holiday airlines that might have served LGW about appearing in OAG or not, so do be careful about that. But the OAG Is really your best bet.
OAG's are monthly (some versions were actually twice monthly in the past but I don't know if that's still true) and are usually very accurate. The problem for you is that it will likely be very difficult to obtain the dozens of OAG's for such a long period. People who collect them are not likely to just give them away. Some people sell them on ebay or similar places but it would be rather expensive and you might only find some. And people who don't save or sell them have long since thrown them away. Even if you do find someone who has all these who is willing to lend or give them to you, it would be a pricey thing to get them to you because of their bulk.
Years back I got an OAG "electronic version" on disks in a trial offer, and so it is possible that perhaps this could exist for your time period. My concern about this, though, is that even if it does exist you might run into the same issue where most people threw obsolete ones away, and people who did keep them all this time are not willing to give them away. Ccollectors of stuff like this tend to be more into the physical, tactile aspect of it than just the information, and I've never seen anyone selling OAG disks -- only hard copy. It's kind of like the market for collectable timetables. There doesn't seem to be any active market for people selling photopies of old timetables, even though a photocopy could contain all the same information as the real timetable does.
In my opinion, you have a couple of options:
(1) If you are looking for things like numbers of flights, numbers of passengers, what airlines flew, etc, you *may* be able to find data like that in some online database. Here in the states there are online stas for US carriers with that kind of information, but I don't know about the UK. If you are looking for things like specific flight times (like, say, you're working on a project on noise around LGW
and it matters very much what time flights are scheduled for ) those type of stats might well not have it.
(2) You could settle for sampling in the period by obtaining certain OAG's, like trying to get a July and a January version for each month of your period. Definitely not as accurate as obtaining every one, but it might be a more realistic goal.
[Edited 2013-02-15 06:56:33]