Ri 5,
Interesting. I have not done the IMC or IR, but a few people I was with in the states have done exactly that, the FAA IR I mean. Good thing about it, is that once you have passed it, you can fly IFR all round the states, fly airways, instrument approaches etc. Personally, I see no harm in doing this, however, someone who knows more than me may beg to differ.
With regard to the 25 hours of instruction bit, I think that is a great idea. I have recently returned from the US after hour building and licence revalidation, and spent around 10 hours with an instructor. I enjoyed the 10 hours with the instructor more than the burning holes in the sky for 30 odd hours. This was simply due to the fact the instructor made me work hard, and did not allow those bad habits to set in. Like I said I am not instrument rated, however we did a couple of ILS approaches and VOR tracking which was a good experience for me. On saying all of the above, I would imagine your 25 hours of instruction would depend on the quality of your instructor. Whilst in the US I was lucky to have one that took the professional approach, which rubbed off on me. Even though I had nearly 100 hours under my belt before I arrived, I actually felt that I came away with quite a few new skills

. I still have those dam checklists imprinted in my brain!
We are always learning!!
By the way, I was too flying the Warrior, good aeroplane!
Also, I am not sure what the benefits are from holding insturment time in the US is, i.e. validity in the UK, that is a CAA question.