I made the jump when it was still JAA. So did my hubby. I *think* the validation (ie 2 exams, 3000 hours, 1500 hours in command of +30 tonne a/c) has gone now it's EASA. I haven't checked so I may be wrong.
Generally within the UK, easyJet and Ryanair tend to mainly take low houred guys. There is the exception every now and then. Other airlines view experienced folks as acceptable. There has been hiring lately but as you well know, hiring is a boom/bust cycle.
I don't know your hours but it's safe to assume you'll need a medical, the 14 exams, a flight test. If you have 500 hours on a multi pilot a/c, use that one. Ideally one that has a sim in the UK. Yes, you'll need some revision as EASA/UK do NDBs slightly differently to Australia. (speeds mainly). Yes, organising a sim, a crash buddy, an instructor and the CAA examiner is a pleasure that only the most sadistic of sadists could dream of.
Good luck.