3-4 months for an IR course is utterly unacceptable. I did mine in 6 weeks.
The school I went to often served as a place which took guys & gals from other less reputable schools after they realised that the training was second rate.
For them it seemed quite straightforward. I think at licence issue time, the CFI would write a letter to explain the switch to the CAA.
It never ceases to amaze me just how many dodgy schools there are. I was recently chatting to someone who explained that during their IR they had no classroom time at all, all briefs were done during the taxi. He explained that when he was taught to scan, the instructor just said 'you'll pick it up as you go along'. Unbelievable!