just chill be yourself don't lie about anything they ask you as they will no anyway and just want you to confirm what they no about you.
cuppa tea and a nice hob nob biscuit seemed to do the trick well it worked for me
make sure you got your cabinet bolted in and your shooting permission to hand and its up-to-date your visit will last about 40 mins to an hour well mine did ,.,.
the visits not the worst part...
the worst bit is waiting for the cert to land on your mat after you been granted it now that can take time
if you got any questions to ask him, ask him he is there to answer an