I guess the easy thing to do would be to copy the 'Default object view...' template to make an override, but I can't find that template anywhere either.
I think I've found it at standard/templates/node/view/full.tpl and so I'll create a copy to override that then edit it to suit my required layout and see how things work out.
That's a top tip :) I've never really read too much from the debug info when I've used it in the past and didn't realise it contained info about the templates etc...I guess I should pay more attention to it in the future.
