Air traffic would have to work it out as well and why should they be better at it than you? probably liability issues as well if they get it wrong. Actually, very easy to work it out -take the angle off the runway and apply that to a clock face, i.e. 30 degrees off is 30 mins so half way round, 40 degrees is 40 mins so 2/3rds round and that is the amount of total wind to give you Xwind component - over 60 degrees the difference between actual xwind and full wind is no worth worrying about - and you are on the safe side!