Hi Jim,
You could have a look at the census info for your family, which might give some more clues. A quick glance at 1891 shows them living in Edge Green Lane, Golborne (which is near Ashton). In 1901, your grandmother was working as a servant in Fence, near Burnley, quite a way away, and her parents were living in Westhoughton, about 10 miles? from Ashton. The adddress was Woodlands, but next door was a property called Park End, and on the same page was Park Farm, which could be the 'Back End Farm' you mention?
I'd suggest you try to trace descendants of your grandmother's siblings as listed on the 1891 and 1901 census entries, perhaps using BMD indexes to find their marriages and children's births post 1901.
Cheers,
Phil