Presumably if there is an automated METAR available for the closest airport then there would have been a TAF as well??
If I was faced with a 200' forecast cloudbase, a private landing site with no aids,a north easterly airstream in Spring in the UK(read fog), temp and dewpoint so close or forecast to be close, my first question to the boss would have been about which hotel we were staying at.
How many holes lining up in the Cheese do you need before you say no. I am presuming it was an IFR 355F2??