Chilli Monster,
I realise from a practical point of view that is the case, but as the rule is stated in the ANO then it is legal. As a rule of thumb then yes but taken literally from the book it should be legal. However...when something goes wrong how liberal can your interpretation be?!
As well as ATCO'ing I've been flying for about 10 years and encountered this kind of situation alot. If the specific met conditions are to be taken into account then things like operating levels should be taken into account in relation to cloud base/tops. Also the metars are specific to within 8km of the reporting aerodrome, so what weather do you take into account to apply the rule? A forecast which may not be accurate, a metar for the nearest airfield or your own estimation considering you may not be a qualified met observer or forecaster?