Not all 747s go to Pier 3, otherwise known as the Satellite. Before Pier 3 was built, the stands on the northern face of Pier 2 were also configured for the 747 (still are), in the days when Cathay & Braniff etc were regulars. We can also accommodate the 747 on the 'end' of Pier 2, several stands on Piers 4 & 5 (North Terminal) and quite a few remote stands.
Perhaps the reason why it appears that most 747s go to Pier 3 is that the only large-scale user of the type now at LGW is Virgin Atlantic. Their Handling Agent, Groundstar, have a number of Pier 3 stands set aside for their use.
British Airways used to operate a number of 747s at LGW in the North Terminal, but in common with many other operators, they now use the 777. The north face of Pier 2 is usually fully occupied in the mornings with 777 and A330.
In the Summer, you might see the return of the Air Atlanta 747s doing charters to Sandford and Sharm el Sheikh.
You will also see the odd 747 parked out on the remote stands, if there is a big enough gap between its arriving and departing to make it an incinvenience on a pier-served stand.
We have around 35 stands at Gatwick capable of taking the 747, but really the type doesn't suit the operation of many LGW-based carriers.
Cheers,
The Odd One