- I'm not sure what a 'standard route' is on a two way route? To me, flying east on the 'south bank' would be the correct path unless the Rules of The Air are changed in the Heliroutes?
The heliroutes have their own specific rules. Helicopters are normally to be flown over the centre of the river where it forms part of the route, unless told by Heathrow Special to fly "northside" or "southside", in the event of opposing traffic needing to pass.
Here's a link to a CAA page which shows some relevant information and a basic chart of the routes:
http://www.caa.co.uk/docs/7/EIS%2006.pdf