Getting close! This is number 3, and it's almost there.
It rolled without cracking, but it was a little sticky still, so it stuck to the paper after I rolled it, giving a not very impressive looking exterior. That's fine for a yule log, as you cover it with more of the chocolate filling, but for a swiss roll it doesn't work so good (hence all the powdered sugar to cover it's sins).
I think this recipe just cooked a few minutes more will be perfect. I've at least got the filling right. I've worked out that it needs to be thick so the sponge doesn't slip, but not so thick it pulls the sponge apart when you spread it. Also, timing is important. Cold filling on hot sponge liquifies easily, whilst trying to roll sponge that is too cold is hazardous.
And, you've got to get the thickness right before it goes in the oven. Thin bits of sponge don't work (I had to roll this from a specific end as it ripped when I tried to remove the backing paper).
I'll get it next time, though next time will have to be in a month or so, as I'm cutting out chocolate for February. What with all the experimenting I've eaten way too much of the sweet stuff recently. My waistline is complaining.