I had not heard about the trial, but March is a long way away and I would probably have forgotten about it by then if I was told now.
250 below 10,000' is a good idea in my view. I am amazed how often an airprox is preceded by the words " no ATC speed restriction".
Maintaining 250 Kts will not only give better spacing, it will reduce noise, get us above the 4,000' noise restriction sooner there bye allowing us to leave the SID on a heading for a shorter routing particularly on LHR northbounds.
Will this mean we can reduce the departure interval on the Detling/Dover LHR departures?
So , yes this one gets my vote.