Hello there,
This may not be relevant but:
1. Like advised, try asking high school direct or we have access to the state schools desk via International office of the WA Dept. of Education (DET).
2. Transfers are fine....timing can be tricky with different academic year timing, but the DET will know exactly re. UK students.
3. There are alternative university pathways, e.g. after year 10 anybody can enter the TAFE (Technical and Further Education) or Vocational Education & Training (VET) system. From TAFE there are pathways to university 2nd year (or 1st) so university applicants do not need to enter direct from school (and TAFE fees for Australians are cheaper than university)
Cheers,
Andrew
Cert IV, B. Bus. & M. Ed.
http://www.aiec.biz