Topbunk - No, not at all. The distance to touchdown at Heathrow depends almost entirely on traffic ahead and not necessarily on the altitude of the aircraft. Obviously if someone is way too high then adjustments are made but the pressure to maintain the spacing is such that some a/c have to expedite descent and others might get a few more miles than their range suggests.
The directors know the ranges of those on the ILS and the spacing required (taking into account VORTEX, weather, etc) and simply add the gaps to produce the range from touchdown. Allowance is made in the calculation for the fact that those on the ILS are doing 160, those on base 180 and those downwind 210. With experience it becomes quite easy.
I'm sure that my ex-colleagues will agree...