Thanks for that. The code is not far off what I had, but I think I wasn't calling it right.
Now I'ev got the whole thing within cache, so the call goes to this function, checking for existing cache, each time. I'm guessing that's how it should work.
I've also change all the static variable to use the c# 'Properties' feature, using get and set, as that seemed to be the approach recommended by most online advice.
Hopefully there is a performance improvement. If not, I'll have to re-look. It's hard to know from my own testing as not sure exactly what I'm expecting performance-wise.
EDIT: Matt, can I use static images of Julia and Sylvie from the Conversive Character folder (julia_smile_quiz_full.png and sylvie_quiz_smile_full.png) on my website? Not sure where I got that folder from, guess I must have downloaded from this site at some point. No problem if I can't do this. It's only temporary anyway until I get my own bot finished to put there.