You would either have to really enjoy learning, or be a masochist to do the ATPLs now there is a viable alternative.
If you go down the CB IR route, you have a lot more flexibility.
So, do the IR(R) and your Night Rating (you need both).
You must have completed 25hrs post PPL flying before you take your IR(R) test anyway, so add in some other flying.
So, now you're 30 hours post PPL at this point and have an IR(R) and a Night Rating.
Do some IR flying with a mentor now - 10 or 20 hours perhaps. There are several really good IR mentors in the UK, and do some stuff on your own.
Finally, do your 10 hours at an ATO for the CB IR issue.
You need to have 50hrs PIC cross country time logged as well, but you should easily have hit that by now.
It's definitely completely achievable in 6-9 months but will be bloody hard work.