I am an A320 pilot and I was in exactly the same circumstances as your question refers to.
When you do your final CAA IR in the A320 sim (i.e. LPC/OPC); you're then current for 6 months although the IR is valid for 12 months. Of course you will still have to do your 'base training' to fully quailify to operate the aircraft.
However, as I understand it, you cannot fly any other type using your A320 IR. In other words, you must have a valid IR for each aircraft you fly.
Hopefully, the above helps and if I have 'got it wrong' then I stand corrected!
Good luck with the course.
pjumbo
