You can certainly freeze the Lemon Yoghurt Cake for your wedding. Wrap it well in gladwrap and plenty of baking paper and freeze in an airtight container. It will keep for a couple of months.
To stop the cake sinking in the middle - try lowering the temperature a little and baking a little longer. You could also try using a smidgen less raising agent.
Hope this helps!
Guys, what can you say about this list? Are these nice cakes or a nice cake just can't be cheap? Sorry for the offtopic, it's just that my wedding is pretty soon and I still haven't made up my mind