twistedenginestarter has a fair point about the forecast winds in general, though I have no experience of your Met Office.
As you find yourself with some free time aloft on a long x/c
, you could try a "Missing Wind" problem and verify the forecast winds for yourself. I have done that on a few occasions and found the winds to be within 15º and about 7kts of those from FSS.
Often though the winds have changed significantly, especially if you do up your flight plan the night before with 12h forecasts or longer ahead. Then pilotage is how you actually navigate - unless you use radio navigation.
rgds
CB