I wouldn't chance it. The quality of the metal and fixings of a modern small dish will withstand the excesses of UK weather thrown at it, but small changes in final positioning on the satellite will occur following installation, dish sag/distortion and degredation, plus the signal fall off during the winter as a result of rain, sleet, snow and subzero conditions cannot be offset with such a small reflector.
Fit a good design zone 2 dish as a minimum, the difference in price is roughly a tenner, which will alarm the average Scotsman, but the additional cost does ensure reception is stable over the year.