1. Crumble crumbs and margarine together and pat firmly into a 9x11 pan.
2. Combine the whipped cream, cream cheese and icing sugar and beat with an electric beater at LOW SPEED. Don't over beat -- a few little cream cheese lumps makes the cake extra yummy!
3. Spread over the base, smoothing it out as much as possible.
4. Put in the fridge for at least 12 hours.
You can actually leave the cake in the fridge for up to two days... just don't add the fruit until the day you want to start eating it.