I am particularly interested because the our ATC interpretation of the current guidelines is that no helicopter should be allowed to hover or hover taxi within 760 m of a runway where a heavier category of aircraft may have created a vortex.
Yes, that's the same problem that we have. It's because of the word "shall" that appears in the ATC regs regarding wake separation for departing aircraft; ie, there "shall" be the required gap between aircraft. The word "shall" dictates that they must enforce it. Having said that, a previous airport that we operated out of, gave us the advise, but when we replied, "roger, request immediate departure", they were happy to let us go.
On approach to land, however, it's different. Threy give you the recommended spacing, and it's up to you whether you abide by it.