Underbody protection

Hymerb564

Hi we have an Hymer B 564 currentoy pitched in west sussex

the underside is already black (bithuman or waxol or dinitrol not sure) but there are signs of rust and the coating coming off

does any member know of a reputable company in West Sussex area that would remove this and reapply Waxol dinitrol or similar? Also if any member has had this treatment done what in your opinion is the best product

 

many thanks