I think so. However, where are you going to go when the fan quits?
Thats what I love about this place answer a question with a question.... Who cares? He asked if he was legal not sane.
The answer is yes by the definition of law you would be legal if you were clear of cloud and insight of the surface. If you have a non UK issued license you are probably perfectly OK to fly outside of the sight of the surface as well, check for restrictions.
As far as the point on when the fan quits, that is a personal risk assessment. I cross the Alps IFR in an SEP quite often. That is down to my personal acceptance of risk. I know others who won't or who will only do it ME. I wonder how some people work up the courage to get out of bed in the morning......
