Doing a SE/IR is cheaper and I beleive you could start it earlier as you only need 50 hours PIC to start the IT but 70 for the ME rating. From my research you do also have a reduce test when you do the ME/IR if you have an SE/IR as there is no enroute section. The other benefit is that your 3 years deadline to do the IR will be met by the SE/IR but if you have just done the exams that won't be a concern.
The problem I see is that when you apply for jobs you will have to say you have an SE/IR. Even if you are fully intending to convert once the market picks up I fail to see how you can say you meet the requirements most airlines ask for and your CV may well end up going straight in the bin. There will be many applicants for each job with the ME/IR in the bag already.
As for doing the CPL & IR at the same school, there are airlines that like this as it shows continuity which helps the potential employer determine your ability to pass the type rating etc. I would say it will become less & less important though as the ability to pay for your TR and therefore take that risk on yourself seems to be the way forward.
I would also suggest that all this talk of what school is best should be taken with a big pinch of salt. Many people only have experience of one school. Also from my research you can go to the best school in the world but if you don't maintain that skill afterwards you will lose it. Someone that did the IR the cheapest route possible and then after the test flies with some experienced pilots, gains confidence and regularly flies themselves IR SE or ME will be a better IR pilot than someone that paid a fortune to go to the best school possible, but doesnt do any other instrument flying until the revalidation is due.