MrGogetter,
Follow your heart, but take it like a Yorkie - a chunk at a time!
Don't worry about the IR. You only really need it for North Sea work. There are onshore IR pilots, but not many, and there is no market for a low time CPL with an IR onshore.
As far as I can gather, an American IR is worthless over here unless you are flying an American registered helo. To convert you have to start again from scratch (welcome to CAA logic!)
The time to start looking at an IR is when you have a CPL. You can then decide whether to do the IR or an instructors course. The only reason to do an IR course is if the NS operators are recruiting, and then it is questionable. I was lucky and my company paid for the IR.
As for age.... A number of people got NS jobs a couple of years ago and they were 40 ish.
Have fun