Afraid I can't help with parents of Sarah and Elizabeth but did find some references to Elizabeth and Sarah Cawood in Leeds Mercury (apologies if you have this information already).
There appears to have been a legal case (Cawood v Thompson) about a bequest made by the sisters of 4,000 pounds for a Sunday school for boys and girls in the parish of Whixley. It also confirms the dates of death -
Elizabeth Cawood - 20 August 1847
Sarah Cawood - 3 March 1848
There is then a Marriage announcement in the Leeds Mercury of 14 July 1849 for the 2nd cousin, Richard:
On Wednesday week, at Whixley Church by the Rev H Armstrong MA Vicar, RICHARD CAWOOD Esq of Whixley Grange to CATHERINE, second daughter of Mr ROWLING of Ribstone.
Vicky