Hi JSF1
You are right about the 1/3THWC - a typo which is now corrected.
Regarding the 700' RA, what you are saying is not strictly correct. There is a facility known as 'data lock' which freezes the values in the PERF App page. You can still write stuff in but it will not affect the system after 700' RA. The gs mini function is not, however, affected by this and the gust will be added as I described earlier right the way down to landing. It is just that the datum wind (tower wind) cannot be altered after this point - the variable 'gust' is still calculated and added to VAPP and that is reflected in the variable approach speed below this height.
I cannot comment about older Airbuses as the ones I fly are all less than 5 years old. I have in the past flown older ones and they all used the same formula. FCOM 4.3.25 says 'The FMGC computes this approach speed, using the formula: VAPP = VLS + 1/3 of the headwind components (limited to VLS + 5 as a minimum and VLS + 15 as a maximum).' I am therefore sticking to my guns regarding the mechanisation of the function. I hope that helps - thanks for your input.
Cheers
NSF