Leisure battery regulator.

[philipm]

I have a 2003 Westfalia Exclusive. The leisure battery regulator goes through phases of clicking on and off, accompanied by the shrill warning device on the dashboard. It can be stabilised by revving the engine, but the situation is getting worse. Does anyone know exactly where the regulator is and how to get at it? It sounds as though it is somewhere near the fridge/sink area.