Cakes freeze very successfully if you follow these suggestions.
To freeze a Madeira cake allow it to cool completely. Leave the greaseproof paper from lining the tin in place around the cake and wrap in cling film. Then place the whole cake in a large freezer bag. If you do not have a large freezer bag wrap in foil. Make sure you label the cake with the date as cakes are best frozen for no longer than 4 weeks; after that they can begin to dry out slightly. Make sure you place the cake carefully in the freezer. Even frozen cake is susceptible to damage and can easily be squashed by items around it.
When you are ready to use your cake remove it from the freezer and take off all the wrapping. If there are any ice crystals visible on the cake brush these off (a silicon brush works well). Wrap in a new layer of cling film and leave in a cool place overnight to thaw completely before use.
Once the cake has thawed you can split, fill and decorate as usual.
NEVER RE-FREEZE A CAKE THAT HAS PREVIOUSLY BEEN FROZEN.
If you have cake left after a celebration, providing it has not been frozen previously you can freeze it even with the fillings and icing. I like to cut the cake into slices, wrap each slice individually in cling film and then put all the slices in a thick freezer bag. You can then take individual slices out for a packed lunch, unexpected visitors or a little treat.
Kellie XCakes freeze, how to freeze, Madeira cake