FPOBN,
You are starting to mix procedures/questions from across continents and across regulatory regimes, a recipe for confusion.
FAA ATC operates slightly differently and offers more in the way of visual approaches and the handover of separation from ground to cockpit. I'm not 100% sure, but I would expect that that is more what...
In the US, FAA AC 90-23F Aircraft wake turbulence, notes the following;
"a. When landing behind a larger aircraft, stay at or above the larger aircraft's final approach flight path.
b. Pilots of all aircraft should visualize the location of the vortex trail behind a larger aircraft and use proper avoidance procedures to achieve safe operations. It is equally important that pilots of larger aircraft plan or adjust their flight paths, whenever possible, to minimize vortex exposure to other aircraft.
... is aimed at.
Certainly it would be difficult for the pilot to do any of that when in IMC on the approach all the way till touchdown. UK ATC does not state 'heavy' in r/t transmissions.
In your quest for knowledge please don't muddle things up. In a thread that is supposedly about Gatwick, quoting FAA stuff is irrelevant. What is it exactly you want to know? The original questions have, as far as I can read, been answered. If there's something else, please state clearly.