I haven't used silicone yet but they seem great.
Nestle is a dark or plain chocolate. I like them fine but it seems any good chocolate would work. I think Ghiradelli is better. If I were making a cake I would use cocoa powder anyway.
A link to where American's in the UK are finding US products.
I don't know where you are located so these might be out of reach.
http://chowhound.chow.com/topics/732...n_module_small
http://chowhound.chow.com/topics/746...n_module_small
Instant pudding? * shudder* There are other ways to make a cake moist.