right i think i know where ur getting yourself confused.
lets talk about the UK.
inorder to fly for money in the UK you MUST have a CPL
inorder to commence your CPL you MUST have done and passed your ATPL ground school and have 150 hours total time.
if you are sure that you do not want to get an IR you can just do the CPL exams. if you want to do the IR as well you will need to do the whole fATPL. now dont ask me what the difference is. all i know is that just for the CPL its a bit easier or a few less exams. i dont know the full difference as im going into passanger flying which i need an IR for.
to make sure that your fATPLs do not expire you MUST finish you CPL AND IR before the 3 years are up (ofcourse if you only want to go into VFR flying dont worry abt the IR).
saying that you are going to restrict yourself to what jobs you can do if you do not have an IR. there are probably jobs out there but there is no money in it and there is very very limited stuff you can do. another thing you can think of is go into instructing as you can get a job the same day you pass your FI course. but again in order to progress to make some good money in that you will need to teach the ME and then IR once you get the experiance. needless to say you will have to have the qualifications before hand...
now if you decide to to do your training in canada they will have different training requirments. this may be why you are getting conflicting info.
an ICAO licence will be accepted back in the UK but you will not be able to use the privilages of your CPL and IR from another country in the UK unless that country is a member of the JAA (canada is not). you will have to do the CPL and IR in the UK again if you wish to work here at a later date. you may be able to get a few hours knocked off the minimum you need for the course but thats it if you have a different countrys rating.
an ICAO licence will only allow you to fly in another ICAO state, in the states aircraft within the state only. for exaple, you will not be able to have a canadian licence and fly a UK aircraft to france, but you will be able to fly a UK aircraft around the UK.