Can't speak about arrivals into LGW but into LTN, the retention of high speed beyond the SLPs frequently creates problems for both the flight deck and Essex Radar/Luton Radar because of the hopelessly inadequate airspace which causes a bottleneck and an inability to get the aircraft down to 5000 feet from which point the intermediate approach is flown.
Whether you're being offered a 'direct' approach i.e. without being required to route into/via LOREL or are following the full STARs into the hold, keeping high speed i.e. significantly above 250 knots will simply screw up your descent profile because Essex/Luton just don't have the lateral airspce to accommodate high-speed manoevring which is why you're so often requested by them to come back to 220.
The guys further back who offer you high speed or who respond positively to flight deck requests are obvioulsy trying to assist but because of the airspace configuration and the interaction with departure routes from LHR, LTN and STN, even when there's no holding traffic, ignoring the SLPs ultimately, isn't that helpful.
A partial improvment to the airspace might - subject to NIMBYs and NOPEs - be introduced next year (An Airspace Change Proposal has been worked on for nearly five years [!!] and is now in the final phase with the CAA) but it won't address the lateral restrictions of the airspace around LOREL or the need for LTN arrivals via LOREL to be level at 5000 feet before commencing the intermediate (radar-directed) approach.
Further improvements are planned for 2008.
So "no ATC speed" will still not mean that "high speed" is necessarily a sensible choice to make and could still screw up your approach, big time!
