I found an easy way on the beach and that is to lay the mast on the ground sideways from the boat. Attach the forestay and one of the shrouds on the highest settings on the plates and then by tipping the boat on it's side and lifting the base of the mast I can sit the mast into it's base and then simply connect the other shroud (which is on the higher hull). Once connected the boat is simply "capsized" on land and it's just a case of pushing it back upright.

The one thing is that the trap shock cord needs to be disconnected before this can be done, but that takes only a minute to reattach.

Once righted, you can adjust the shrouds to suit the conditions and preferred mast rake. I reckon that it takes me about 4 mins in total to solo raise the mast this way and I don't need any special gadgets.