Hi Fran
Unfortunately verrucas can be long lasting due to the lowered immunity; possibly your bog standard over the counter preparations aren't suitable for you. Also you do have to be careful what you use when on strong RA drugs as even creams and lotions are absorbed into the system and can interact with other things. It would be worth seeing a podiatrist to get them sorted once and for all.
In RA, the feet can become easily damaged especially when you consider how much use they get! It's not uncommon for the metatarsal heads to become inflamed and sensitive as well as the small joints, any knock however small can be very painful . Worth getting a podiatrist to take a look ... you only get one pair of feet so they need a bit of TLC

Hope you manage to get the problem sorted!
Lyn x