Basically you've got the top switch with an LED function. Although expensive, a shop like Maplins would be able to find you one in their shop. To know if its the right one, bare minimum (if you want to monitor two batteries) is a switch (diagram 2) with three terminals where at least two terminals have continuity (you can use a test meter for this), whichever way the switch is er....switched. The ideal is one that has three clicks, the centre one being off (as in diagram 3).
I'm making all this sound far more complicated than it actually is, since if you have the right switch its really easy to fit and connect up. The diagram is just a simplistic way of explaining how it works in relation to the switch. The circuit itself is very simple.
The switch you have now is ideal for switching something you need to know is on, such as a rear window demister or a fog light. In fact you could if you want, just monitor the leisure battery using the one you have, but I guess you'd feel sold short then and yearn for the five star version like us toffs.
If push comes to shove, print the diagram. Many Maplins stores seem to have an 'experts' counter at the back and they'll know exactly what switch you need. The only difference between diagram 2 and 3 is that the latter enables you to switch off the meter completely (not that it uses that much). In diagram 2 you'll be monitoring one battery or another all the time.
Mark
