Need to hire somebody to fir a waste pipe

Not a cheap option but try a local plumber ?  It's all plastic pipes sockets etc.  With luck you might find one that has a caravan or Motorhome ;-)

rgds

Post your problem on facebook - bet you get offer of help ( chargeable or not ) very quickly. 

Google - Mobile caravan engineer (and then the town where you live) and you should get someone who will live near you, and will come to your home.  Basically, most internal bits of a motorhome are just the same as those in a caravan - but you obviously need the 'motor' bit of it serviced by someone who services motor vehicles.