Damp meters

just bought one today and tested it very good valuebassett

Bought one today also - parents bought one too....so did my sister!

Weymouth & Dorcester branches have had any only the digital measuring devices otherwise I would have purchased one.

Just go on  Google all the makes and models and prices. 

cheap enough to hire from a local tool hire shop too. that's what we did.

Just a point, the damp meters that use two prongs (almost all) Measure dampness ON THE SURFACE ONLY, they measure the resistance to passing current from one prong to another. In a house or caravan there's always a condensation factor ie humans and so if after storage or even just using the caravan you'll find a substantial reading (if you think it's bad try your house !). Best not get to wound up, just use a small dehumidifier during the worst months of swingeing temperature changes (normally Feb-April and Oct-Dec) you can reckon that any more than a 8 deg drop will start to breach the "dew point" (where the changing temperature causes the heat in the air to condense on colder surfaces). I use a humidifier with a 250w motor and for the costs involved (very small, I allow 15p for every kW hour) it protects the considerable investment in the caravan that many of us have made. Obviously any dehumidifier cannot prevent water leakage through body seams or surfaces, constant vigilance is required, I check every October (visually) in case I find dried out sealer or signs of moss in seams, (8 year old van, non found so far).