I don't think Imperial will be able to answer you as they don't actually do the conversions themselves. A company called Autovan Services
http://www.autovan.co.uk/ actually do the conversions.
Anyway, I couldn't wait so I have done as suggested and switched things on and then pulled fuses to see what's connected to what. the result is from left to right: -
1. 12V Socket (above mains socket in side of kitchen unit) 15A (Blue)
2. Lights (downlighters) 10A (Red)
3 Gas Ignition 7.5A (Brown)
4. Tap / Pump 10A (Red)
5. Tank / Battery gauges 5A (Tan)
6. Battery charger (off mains) 20A (Yellow)
Extra fuse above and to the right of other fuses = Fridge 10A (Red).
I also had a look at the split charge relay under the bonnet today too because it wasn't charging the leisure battery when driving and as I was trying to make adjustments to the relay it kept switching on and off repeatedly. The reason was the main feed from the positive side of the starter battery was only just making contact due to the fact that the installer had only crimped the plastic outer sheath onto the cable, the metal connector hadn't been crimped at all and just pulled out! I remade the connection properly and now I need to wait until tomorrow to see if it charges on the way to work.