You can be fairly certain about UK weather at +3 days and pretty much accurate the day before
Helicopter Redeye forgive me for asking but are you on drugs or do you work for the met office??
The Met offfice do a very good aftercast, a fairly good nowcast but the forecasting still leaves something to be desired! I have had to ring them on more than one occasion to question the TAF at an airfield when they were giving 5k+ viz and a 1000 ft cloudbase as the worst expected weather and the airfield had been sat in fog for the morning!! On pointing this out to them an amended TAF was issued which gave the fog as a temp.
bit off the initial question! My limits 55kts to startup, and 250 ft cloudbase and 500m for landing.