pax,
I mean they cannot fly the approach at Vref plus 60 just in case the wind chooses to vanish at some point can they.
Well, they sort of do!
Ground speed MINI function on the Airbus in strong headwinds mean they actually speed up (in terms of ground speed) when compared to other manufacturer's aircraft. It's all about maintaining a certain energy state.
Here's a basic explanation of GS-MINI from Chris Scott on PPRuNe back in 2008.
Now: let's take the sea-level ISA case, where IAS=TAS; a Vapp of 130kts; and a predicted headwind of 10kts entered into the Performance page. On a conventional aeroplane stabilised at Vapp (130kts) at a height of 500ft, if the headwind is 30 kts the GS will be 100kts. But when it comes over the threshold, where the headwind is only 10kts, it will need to have accelerated to a GS of 120kts to maintain the required Vapp of 130. This will require a lot of extra energy (from the engines), which may cause problems, particularly if the loss of headwind happens suddenly (like at night).
It makes sense, therefore, to ensure that the GS remains at or above 120kts throughout the approach, even though this initially results in a higher IAS (150kts at 500ft in this case). The "managed" speed (IAS) target on the ASI (used by the pilot and the autothrottle) goes up and down with the headwind, but never below Vapp. Reaching the threshold, provided the actual headwind equals the predicted figure, the speed target will be Vapp. If the wind is higher, the speed target will be above Vapp. This should not be a problem for stopping in the runway length, because the GS will be no higher than originally planned.