Thank you all for your replies!
Yes, Todmorden is very confusing re the Lancs/ Yorks thing. And I found a record last night which seemed to suggest it was in the Parish of Halifax, where usually it's in Rochdale, just to add to the confusion...
I like the 1816 marriage - a possibility perhaps. One of Grace's grandchildren by her second marriage was christened Sutcliffe, so that would be very neat if that's right.