There were very few rag wing Hurricanes left at the start of BoB. The metal wings were a vast improvement, performance wise, on the rag wings and only took a little over 3 hours to convert to.

As far as a fire goes, it's (just) my opinion but I don't think a fabric wingtip or aileron at flying speed would catch fire without a good fire already going in the wing, assuming it used butyrate. (I'm a mechanic/pilot who's worked extensively with fabric aircraft so I'm ... an expert - lol) And as far as aluminum goes, it would likely be an unusual situation (in this context) where an aluminum alloy catches fire.