has anyone invented an easy way of single handedly stepping the mast, maybe using a tabernacle or similar

If hog steped its easy just keep the bow angled down (chock the boat/trolley) lift the mast verticaly outside the boat & lift/slot straight in.  If deck steped lay mast in boat, connect both shrouds (on max length) again bow well down.
lift mast up & in to step, the shrouds should prevent the whole lot falling out.I have had a spare piece of line pre-tied off at the jib tack 
then laid back along the foredeck close to hand ready to lash round the mast at gooseneck level (where it can't slide down!) to hold the rig on a temporary basis until you get out the boat & finish rigging. I've also tried fixing the main halliard forward & holding the rig on that which also works.
Caution! The later is done by standing in the boat & requires a certain amount of upper body strength/nerve. It also requires your boat to be up to it!  Don't attempt if unsure & make sure all other bits of line are taped up out of the way. Hope this helps regards Barry

Sean, We will be at the club Wednesday morning about 10.30 stepping ours and going for a sail if you want to have a look. 
Barry's right dont even think about standing in the boat while its on its trailer.
PB

thanks for tips,all helpful.
paul im of wed so will pop down and have a chat as i have a fair few question if i can get away from baby sitting dutys.
i have stood in my boat on the trailer and all is well so must still be in good condition