number_6 has an excellent point. Based on today's exchange rate, here are the *ONE5 current fares for first, business and coach, ex-Egypt and ex-UK in GBP:

Egypt 3305/2565/1200
UK 7419/4919/2119 or 1919

The two coach UK fares are for high and low season originations, respectively.

Even though you aren't going to take the trip until 2004, you could travel to CAI now, buy your ticket and take the first segment, CAI-LHR. This will lock in the fare in case the EGP strengthens or OW raises the prices ex-CAI, as they did ex-JNB when the Rand crashed a couple of years ago.