I'm in the same position as jennyb - nothing we have tried keeps them out. But depending on the aspect of your garden, you may be able to avoid having to put in a higher fence by making the one you have got impossible for the deer to see through. They don't like jumping blind, so if they can't see what is on the other side they may be deterred. It worked for part of our garden, but they found other ways in.
I also net all my vegetables to stop the deer getting in - well nearly all: the flourishing courgettes have just been eaten to the ground while we were away on holiday.
