Joining event (Tour Of London) did not force a world change on me, so I did it in Watopia?! There were around 10 of us.
One would expect to be moved to proper world automatically for scheduled events.
PS: I have won a DqF Watopia group of ToL in solo ride from the get go (not that it matters :))
A similar thing happened to me during the Tour of Innsbruck. I did Stage 1 in Watopia, and it was a lot easier thean it would have been in Innsbruck.
My Tour of London Stage 1 always took me through Box Hill, no chance to change course, or to turn, so I could not finish Stag1, and I have to finish this section on 23.12. probably drive again.