Even easier, see if you can find this in the Latin section of your grocery store:

 
The cooking is already done–no worries about boiling/baking cans of condensed milk or anything.
 
For banoffee pie, it could not be simpler.  Take a prebaked crust (or graham or chocolate cookie–your choice) and place two sliced bananas in the bottom.  Scoop out a can (two if you want it really sweet) of dulce de leche and spread it over the bananas, being sure to fill in the crevices between them.  Whip about a cup of heavy cream with a little sugar and vanilla extract (or maybe try rum extract), and spread that over the pie.  Done!