helo was lost for a while and had to land in snow. !!!
Landing for a while to allow a heavy snow etc to pass is reasonably common, by day as well as by night (though it happens more often to the Scottish SARBoys & Girls) - even if you know exactly where you are, and have the best nav aids in the world (unlike a Sea King!), if you can't see, you tend not to press on!
One would hope that the Leconfield aircraft would not get lost within 15nm of base, though of course nothing can be confirmed or denied...