Very many thanks to both of you – and didn't expect the restore - that's great!
Jim - I agree the older lady does have a particularly strong family likeness. If she were a daughter, she would have to be either Lucy or Emma. If we say e.g. 1876 for the photo this would make her either 28 or 26. She looks older to me but it's hard to tell. Lucy does have a baby in 1876 which would at least fit with the scenario. Assuming this date and the other guesses you make, it would mean the setup is something like:
Back: Sarah Ann? (16), George? (13), ? (maybe Lucy’s husband), Harry? (18), ? (no idea, Mary is only nine which is the only other daughter (~14)
Front: William (47), Alice? (6), Lucy/Emma (28/26), Alfred? (11), Lucy/Emma (28/26), Clara? (5), Harriet (50)
Do you think the lady holding the baby is a daughter or an in-law? Another possibility is that she is Charlotte Cox, the wife of Thomas - they married in 1875 and had a baby in 1876. That baby and the other one mentioned above are the only grandchildren born between 1872 and 1878. And only Thomas and Lucy had gotten married by 1876.
If the older relation sitting isn't a daughter, it could be William's younger sister. In particular he did have a sister who was a lifelong spinster. She was born in 1839 so would have been about 37 in 1876.
Really wish these people had written their names on the photo...!