I used Mary Berry's recipe from here for the roulade. Once it was cooked and cooled I splodged on some black cherry jam onto the roulade before the cream. It was really lovely, not too sweet but very moreish. I ignored Mary's request for good quality chocolate and used value dark chocolate and it was absolutely fine.
I was impressed with Mary Berry's recipe so have decided to try her chocolate sponge recipe (with an added extra of course!) for my birthday cake.