The A320 seeks in 'managed mode' to maintain the groundspeed related to Vref at touchdown ( ground speed mini). At LGW with say a wind of 260/60 at 6 miles, 2000 feet ( not exactly unknown) to maintain a ground speed of say 135 knots, the true airspeed will considerably exceed 160 and this is not acceptable to air traffic in terms of maintaining constant spacing. On the other hand a 747 may not be able to get the flaps out in time with any more than 160 to 4.
NATS would say let the controller know in good time but my experience is that at most times they would have difficulty fitting in aircraft at different speeds. Perhaps we should try it!