In the Uk closed means whatever the airfield owner wants it to mean - it can mean totaly closed, it can mean that if you are a mate of the owner you can get permission or maybe if your dad has just died he might do the same, it may even mean closed to anyone axcept based aircraft - the thing is that you need the land owners permision, if you can get that then it does not matter what the NOTAMS say, chances are that unless there are exceptional circumstances closed means closed - but that does not make it as hard and fast as some have stated