Hello there,
I've found your family in 1891, but they're not in the IOM they are in Liverpool -
189134, Guthric Street, Liverpool, West Derby
Charles Birch 34 Head M Plasterer Liverpool, Lancashire
Margaret E Birch 24 Wife M Isle of Man
Thos. Edwd. Birch 2 Son Isle of Man
Charles Henry Birch 7m Son Lancashire, Liverpool
(RG12/ 2991/ 69/ 15)
Doesn't help much with their marriage though! There's nothing on the IGI

Perhaps if you managed to get a birth certificate for one of her children (born in England), it would give you her maiden name and aid your research
Best of Luck
Sue
