Given that AIC 15/2006 states:
Operations from contaminated runways, by all classes of aeroplane, should be avoided whenever possible.
and
aeroplane performance relative to a particular contaminated runway cannot be scheduled with a high degree of accuracy
and
the use of a contaminated runway should be avoided if at all possible.
May I ask why you would want to take off from a contaminated runway? If you do take off, and an accident ensues, there will be an enormous amount of evidence that you have done the wrong thing, and your only response will probably be that it was commercially expedient.