Got some hooks, and then found out we haven't got the bars on the oven ceiling to hang them from. D'OH! 

Talk about gutting! 

I have that problem too mate.

Move a rack up highest and hang them from it would be the way to go. Not sure if that's what UncleFrank actually did.

You just lift one of the oven racks to the top position. This is not completely new. I posted pictures of cooking char sui pork on hooks several years ago.  It wasn't my idea though and I forget where I originally saw it.  The skewers threaded between the hooks is a good idea, not too different from supporting them across the top of a baking dish and it is certainly a handy alternative for the tandoor.

Hooks? Use an old wire coat hanger - snip to required length & bend to S shape with pliers

That may be fine for suspending skewers but not to use directly on the chicken (or pork), and even then it is depending upon what the coat hanger wire is coated with.  I would suggest an initial heat treatment without food in the oven at the very least.  I originally used 1.6 mm stainless steel TIG welding filler rod but I have since purchased proper hooks from a caterers supply.  They're not expensive and there are good reasons for using correct metals with food.