Specifically it was the reciprocity for me. I'm hoping to expand my scope, at it looks that a move to LAS would limit it further. I think I'm correct in thinking I wouldn't be able to start IV's or give any IV meds, intubate etc until I was an Advanced or Specialty Care paramedic.
Many Paramedics in the UK no longer intubate. This is largely because they cannot maintain competency. Remember, in the UK, Paramedics are professionally registered with standards of competence set by the HCPC and the accountability is with the individual practitioner at the end of the day. The other reason is well, it doesn't really help and there is good evidence to show this. Indeed I think here we are only averaging about one intubation a month per Officer.
You can start an IV as a Paramedic and give some IV drugs yes.
Because of the professional HCPC registration you have very wide scope in what to do with patients and this seems quite nice; i.e. you are a registered professional who can exercise your own clinical judgement (and on the flip side are responsible for it). Australasia is slowly moving towards registration and it's at least one to two years away. While we have similar practices it would be nice to have some legal weight behind it.
I seriously investigated moving to London, and I have personally been to London a couple of times. It is an incredible world city with absolutely amazing things to do and see and that is not even considering the wider England, UK or Europe. Auckland is an up-and-coming world city but I think we are still five years away from truly being there. I'd go back to London in a microsecond, but I just do not want to move there to work.
If you are young and want some experience I can't see why you wouldn't go especially considering the LAS is actively seeking internationals?
Do a Google for the BBC series "Ambulance" and have a squiz; it's on some streaming site somewhere probably. It's three or four very recent episodes that will give you a bit of an insight.