unless it's HPA (high perf), smaller turbine etc, which you won't likely touch during PPL training, nothing to worry about.
With 100+hrs flight time the PPL conversion would be easy. Well, it should be now even with basic PPL without 100hrs, but then the EASA lingo in the conversion of equivalent licenses from ICAO, is kinda vague.
Bottom line, the endorsements, while in countries like SA, NZ, Australia etc, are each make and model specific, even light piston singles, not so in EASA, where you got SEP. With 100+hrs you can apply for adding the class rating to your Euro licence, althouhg I presume you'd do some familiarisation/LST prep which'd satisfy the SEP class rating requirements anyway..
Anyway, you got till April 2014, the ability to use ICAO licence for PPL privileges without any extra paperwork in the UK for day VFR flying, so if you're gearing towards CPL, soon as you get the PPL done, crack on with EASA ATPL theory, sign up for distance study couple months before you get back to UK while in Australia, to speed up sitting the writtens, brush up classes when you get back.
Other than flight proficiency, I don't see point trying to do Aussie CPL if you're not going to emigrate there. You're not going to gain any advantage as low timer without heavy jet PIC time for the theory/groundschool waiving, so it's extra cost and time you'd spend.
For Euro licence, I'd aim for the private and then do some useful solo nav flying, bearing in mind the qualifying XC for CPL and XC PIC time and so on, so that you don't have to do it last minute in the UK or US or wherever you'd finish the rest of PIC time building.