Thanks for your responses.
We had originally looked at the 186 but this appears to present us with more problems.
If we waited for the 2 years (although the notes on the website suggest we can't use the transition scheme because the nomination was lodged before 1st July 12) then our son would need to take a year out before starting Uni. He would then be over 18 so couldn't be included with us and would have to lodge his own application, presumably a relative sponsored, which could take 18 months. So, in effect, he have to take a 3 years break. I can't see any Uni letting him in.
He wants to do veterinary so, yes, the fees are almost £300k. And, as the course is over subscribed, I imagine he'll find it difficult to get a place unless he applies after year 13.
Skills assessment won't be a problem but there's no chance we will be going back to the UK (we wouldn't be able to get the time off work, Oz is weird in that you have a right to holiday each year but employers can insist that you don't take any holiday n the first 12 months - bonkers) so we can't apply offshore.
The notes say you can apply on shore if you have only worked in Oz for a short time - does anyone know what is meant by 'only briefly'?
Does anyone know a good migration agent in the Melbourne area?