Gear box trouble in County Durham

TracyJ

We have a 2001 Mclouis glen 432 Motorhome, on a Fiat Ducatto 1.9cc chasis. Recently it has started jumping out of 5th and now 1st gears. Our usual car mechanic doesn't fix gears. Is this something the service areas of Motorhome dealers can fix, or does it
come under van servicing. We are a bit lost about where to get help in our area. Can anyone recommend someone in the County Durham area? thanks for your help.