HEATHROWDIRECTOR
Interesting you mention speeds of up 340knts into holds and beyond. I assume you are refering to the resident rocket at EGLL, my company policy is to be at 250knts below fl100 irrespective of speed controls being lifted, our flightplans have the departure and arrival speed built into them. Nice to know that some behind me might rear end my APU, but then flying into EGLL is one of the most pleasant flying experiences I can recount. ATC is the most professional, courteous, and expeditious in handling the vast amount of traffic in their airspace. By far the best and efficient.
On departure though, as a bigbus driver, when ATC advise no speed restrictions, we remove the bugs from the FMC and our stupid aircraft slows down to optimum climb speed which invariably is around 190knts to 210knts. climb rate of a slug.