I don't know about Scotland but I'm farming down in Suffolk and we rely heavily on an accurate forcast, we get our weather faxed through every morning from Weather Quest in Norwich then we look at the Met office and the BBC, we find that both of these are pretty reliable, although rain tends to be an hour later than is usually forcast! www.metoffice.gov.uk www.bbc.co.uk/weather/ukweather
I hope this helps, although as you rightly say the weather in Scotland takes some predicting!
Used to be a meterologist in the RN. Stick with the Met Office information, unless you want to interpret charts. Don't rely on anything looking further than 48 hours ahead. The Metcheck 7-day forecasts are infamously unreliable.