FPOS-I is a very very simple, monkey see monkey do course and is in fact pitched at a levle below that of the operational First aider, people get confused about this because FPOS-I includes Oxygen adminstration and may include basic airway management - which for SJA are and have been in the past at the 'advanced first aid ' level.
there is also a sense of wonderment from some people because you have pay money to the IHCD for theceritifcates for FPOS which in their tweisted little world makes them 'IHCD trained' like a 'real ambulanceman'
as an FPOS-I holder the only things that won't require at least some (re)training are
Primary Survey
CPR without adjuncts
there is very little actual first aid in FPOS -I
AED depends on the models in use if your CFR scheme and locla SJA use the same machines great - but very few SJA regions solely use one machine and if they do it probably isn;t the G3 that is the standard ( cheap, tacky and slow but it;s ticks the ORCON box) NHS CFR machine.
Medicines adminstration is nothing to do with cannulation.
there is a reasonable list of medications open to appropriately trained SJA members
-Oxygen
-Entonox
-Aspirin in chest pain
-paracetatmol
-ibuprofen
-an antihistamine ( lorataidine iirc)
meds adminstration also covers the management of hypoglycaemia
the use of patient;s own Adrenaline auto injector in anaphylaxis
I am unaware of any FPOS-I schemes which allow meds adminstration other than Oxygen , it;s the levle 4 / FPOS-Enhanced schemes that allow more meds
Realistically you are looking at around 2 years from walking in off the street to ETA as a volunteer , the reasons for this are mainly to do with making sure people consolidate their experience as first aiders and AFAs and build up some clinical acumen and credibility before ETA /EMT course - as the expectations of Emergency ambulance crew volunteers for SJA are at the same level as they are for a full time crew at the EMT /tech level regardless of whose badge they are wearing
( this is why the EMT syllabus now coming in includes things like 12 lead , glucometry , referral pathways etc)