Winter storage preparation

My motorhome is stored outside at an angle on a short drive way.  As a result the offside receives cold blasts from the Bristol Channel and the rain drains on that side as well.  As a result the inside area behind the drivers seat develops a small area of mould on the wall fabric.  Each years Habitation Check - SMMT be Auto-sleepers shows all reading at 15% or below.  I also use the UniBond Aero 360 which is effective at higher temperatures but less effective once the outside temperature drops below 10 degrees.  It would be nice to plug in a heater but this is not possible.
I am looking for a damp mould preventative spray which does not damage fabric?  

Ideas and suggestions would be appreciated please.

Many mold removers contain bleach, therefore be careful. Ronseal produce a mould killer without bleach, but check if it can be used on the wall fabric.

In my opinion, the best way to avoid mold problems is to ventilate as often as possible on good days during your winter layup.

Hope this helps.

Leighton.