Thanks everyone, these are great and really valued replies, thanks (reminds me how great this website is). We have lots of lime at the moment as we are renovating some listed buildings here so I will give that a go tomorrow, what an unusual tip! (or is it..) Gherty is up and about today looking great so the new medication is working quickly. I must say we have been using both purple and blue sprays, think I'll have a re-check on exactly the make of the blue we are using. So far as the rough ground - we have been keeping them in a quarry, very rocky and stoney, they love teetering on the narrowest of ledges but it does also have sandy patches and muddy bits near the house (I'll get the lime down) so we clear out their feet and nail chop at the end of every month as a rule (is this enough?). Think we'll extend the hard standing around the house by a few meters perimeter and fence it so I can confine her when necessary.
Thank you all - wish goats feet were designed better!