Can someone explain why it takes an hour to switch to another runway that is just a few yards down the taxiway.
Since runway 08R was in use today, taxiing aircraft for the runway would likely be using both runway 26R (as a taxiway, for the 'J7' holding point) and taxiway J (for holding points J1-6). So there would probably be aircraft on the northern runway waiting to depart.
In addition, taxiway Juliet cannot be used simultaneously with northern runway operations, so all (11!) aircraft at the Juliet holds would need to be moved, probably onto the main runway, to completely clear the area.
ATC then also need to secure the protection areas for northern runway operations, and the runway needs to be inspected to confirm safe operations can commence, a process which in total takes around 15 minutes.
Combine this with a (possible) stranded aircraft on the main runway and an ongoing hydraulic spillage incident, then you can realsise that to have it all up and running again within an hour isn't actually as bad as it sounds.
If you're not familiar with the LGW taxiway layout this chart will help you understand that it was not likely to be a simple 'shuffle' of aircraft at the Juliet holds:
NATS/AIP Taxy Chart