It's always more difficult in hilly areas because the weather travels up the valleys. Kent weather forecasts were depressingly spot-on, not just because it's in the SE, but also because there aren't any significant land forms to divert the weather. If it said it was going to rain all day, that's exactly what it did.

Is there a met office mountain area forecast that covers your area? Is it any good? I find the met office Yorkshire Dales mountain area forecast is pretty good. My only irritation is that it doesn't switch from "today" to "tomorrow" until about sunset, which means you often have to leave decisions quite late.