I always saw the IMCR (as it was when I did it) as an essential part of the PPL anyway along with the night rating. I did mine almost straight after I'd done the PPL, I think before I even took up my first passengers. So I haven't really any experience of not having an IR(R) but I would certainly say go for it, how can it possibly be detrimental to your flying? With the caveat of course that you need to keep in practice.