Yeah, I found the prep day quite helpful and I'm glad I paid for it.
As for the IR test, I suppose it depends on how your rig is set up. On the rig I had the supply neutral didn't have it's own pole by the mains switch and it also didn't have a screw terminal, as you would expect, to allow me to disconnect it, so I asked if I could disconnect it for my IR test but was told it wasn't necessary as it was already isolated where I had locked it off all of a few centimetres below the mains switch on the CU. As for the earth, I left that in for IR and I think you have to because whilst doing an IR test you are putting a voltage through your install and if a fault is present then the install surely wouldn't be earthed for a 'gobal' IR test. This is also the way shown in the OSG, i.e. the main earth is still connected. Not sure if that is what you have been told on your prep day, but that is what I did on the day of my assessment. I only disconnected the main earth for the Ze test and then I connected it back up immediately after that test.
One other thing concerning IR: on the ring circuit you have to connect a spur up that has no load on it. There was a neon on the one I had that I couldn't remove as it was on the top of the switch so I tested it's IR with the switch in the off position so it couldn't be damaged. Be careful about this as it is a simple mistake to make when you're rushing.
