Thanks for the all of the replies.
IO540, I called Simon Oliphant-Hope who wasn't around so I spoke to Jamie, the guy who did all of the flight planning for his trip and was very helpful. They were IFR so he wasn't certain exactly how VFR worked there but thought that it still involved IFR clearances (your routing is security led), so would require an IR which I don't have yet. He also confirmed the high charges - over $1K landing and handling charges for an overnight stay in St Petersburg! And they had to have an official translator (so it looks like you can't just take some nice Russian student you've met in a bar in London!), who acted as navigator and did the R/T although the requirement again seems to be for security reasons.
So I think as Robboflyer discovered for a 1/2 day trip it's a lot of work but probably worth a longer trip at some point.
Thanks again everyone for the help.