Ok, before commiting money to it all. You have to realise that you'll be living in the UK or Europe somewhere. Can you handle that? If you don't like the idea of living in the UK regardless of the job then don't go through the pain.
Get totally familiar with the CAA's website, in particular personal licencing and read the LASORS section G (ATPL). Print it out and go over it with a fine tooth comb.
The initial medical here is a smidge tougher than the Oz Class 1.
I have been saying that turbine time is useful to get ahead because there are thousands of low houred guys here looking for a job. As in Oz, here they tend to employ folks they know/done this system.
Can you get a job? I honestly don't know. I do know that it isn't a walk in the park unless you have turbine and pref jet time. That is a definite known.
To minimise your exposure to risk I would investigate doing it via distance learning and see Bristol Ground School for their course. You MUST come here for the brush ups though.
After the 14 exams you'll need to do a min of 15 hours (sim and flying) to convert your IR over. What is after that I don't know. LASORS should have that answer somewhere. As for the course in Spain, I know nothing about it. (regs have changed since I started it).
If you don't have +500 hours in multi pilot aircraft then you'll more than likely need to do a MCC course. Budget more money for that.