Instrument flying is definately a good idea. In fact the further North in the UK you go, the usefulness of IMC or IR increases with the square of the co-efficient of lift! (or something!)
Seriously though, I would reccommend an American (FAA) Instrument Rating. You get 40 hours flying for about £400 more than the 15 hour UK IMC course! Also it will definately help when it comes to the UK IR.(Believe me, I Know!) Also with an American IR, you learn stuff like limited panel non-precision approaches, which you never do as part of the UK IR.(although adds lots of grey hairs!). You also do airways section which is omitted from the UK IMC rating. I am now an IMC instructor, and would still reccommend the FAA IR to anyone who intends to complete th UK IR sometime.
At the time I completed my FAA IR, the CAA issued an IMC on that basis (for the appropriate fee, of course), and you were exempt from the fully approved UK IR course.
I believe that this is still the case.
As with any training establishment in the States though, choose you school carefully! I completed mine at Air Desert Pacific, La Verne Airport, nr LA. Weather was proper IFR, and staff and Instructors very professional.
Good Luck!