Wow, that was quick! Thank you ever so much for your help. The gravestone is not very clear, but it definitely doesn't say Joseph Hughes which is strange, unless Joseph had a brother and she married him also?
The rest of the family are correct, re Solomon, Elizabeth and Margaret, although Margaret's name is also unclear, but the dates match perfectly. The corrosion has definitely thrown up a mystery for me, but you have helped immensely, so thanks again.
Paul