For practical purposes Code Blue has given you the most accurate and informative answer.
Use an average wind for each leg for the altitude that you intend to fly at. Interpolate from the windchart.
If you decide to embark on very long nav exercises once you have obtained your PPL then you can always break the long sectors into 2 or 3 parts, particularly if the wind varies dramatically eg through frontal systems. Worry about that when the time comes.
Some days the charts are more accurate than others, which is why you are going to learn all about track error & correction angles and the 1 in 60 rule.
GOOD LUCK, but most of all enjoy the learning experience!
