All sounds sensible to me. The only thing I would say is that you really do need to be on the ball for the IR. I would be tempted to do the hours building first so that you are more experienced when it comes to the radio work/visualisation bit. For example, knowing the aircraft intimately will be of enormous help in reducing IMC workload. If you know that your aircraft requires 1900rpm for a 450' a minute rate of descent and 1700 for 550 then already you are ahead of the game. Similarly, with the multi, knowing the power/prop settings for various speeds/rates of descent/including single engine will also be of help.
That said, if you have already done the IMC rating, you should be able to cope with the FAA IR without too much of a problem. It is much more challenging but if you know where you are in time and space then you'll be OK.
One final thought. I did the CPL written test in UK before I went. It is good to get it out of the way early. I would not try to do this with the IR written test though. In many ways, the IR written is much more difficult than the CPL. You also need to experience FAA rules and regulations and fly a bit in the States before you will understand the questions.
By the way, I have all the Gleim FAA test prep CDs which I found invaluable. (IR, CPL and ATP). they cost me £69 each. Would you like to make me an offer?
Good luck.