Cottam,
Our Heli aiming point is 250m from the edge of a nominal Code E runway, and is considered vortex independent from that runway, unless it's being used by an A380 (then 3 mins applies).
The taxiway some helicopters use to get to the HAP is only about 200m from the runway, but as we have been using it for hover taxying for years and years without incident, CAA were happy for us to continue using it as such. No wake separation is provided.