Going to a learn to surf camp is a great idea. There is information on learn to surf courses on the BUG website and in the BUG Australia guidebook. Surf schools also advertise in backpacker magazines like TNT and British Balls.
An International Driving Permit is just a document that extends the time you can drive outside your home country before you need to apply for a local licence. It does not replace your existing licence and it has to be shown alongside your licence from home. You can get them from auto clubs - in NSW you will need to contact the NRMA (website
www.nrma.com.au). You may need to apply through the AA or RAC back home - you should be able to download the appropriate forms from their websites (
www.theaa.com or
www.rac.co.uk) and apply by post.
I doubt that you would be able to use an International Driving Permit as ID at clubs and pubs. You would need photo ID such as a passport or a drivers licence with your photo (like an Australian licence).
It is possible to swap your current licence for an Australian licence, but this is generally not worth the trouble since you'll need to apply for a British licence again when you go home. I would probably just keep using your passport (unless you have a photo licence from the UK).