You could just ‘eyeball’ it and look at the
answers: something from the southwest at about 60 knots.
Or
you could average the winds shown on the chart:
Just
after departure 230ºT/95
At
005ºE 230ºT/55
Approaching
London mean of 245º/35 & 220º/40 232ºT/37
Mean 230ºT/62