I'd guess that anything they sell in chippies must be mass-produced and micro-waveable?

Untrue! Babbies Yeds are still kept in a double boiler in chippies near us and pies are cooked in the oven and kept warm in glass fronted case above the range. The pies can get a little dry after a while but put a good ladle of gravy or curry (with raisins!) on and they are fine again:-)

Cheers

DeG