Best advice I can give in this situation is to plan effectively. It made sense for me to go to Riverside, get an FAA IR, and then return to the UK to convert.
I started off by choosing where I was going to do the IR in the UK (I chose BCFT, Bournemouth). They use BE76 Duchesses for IR training. So then I looked at doing the FAA IR, and I only considered schools that would (A) provide accomodation and daily transport, and (B) use BE76s. Obviously quality of instruction was what eventually decided it for me, and I heard on the grapevine telephone that Riverside were good.... sold.
Although BCFT were very good indeed (Big Up M.B.- good luck with BAS), I would recommend that if you are going to reduce the cost of your IR by going along the Riverside route, and do an FAA IR and then converting it, you use Airways to do the conversion. The reason I say this is that the two schools are used to each other's training methods, checklists, procedures etc etc.
As far as doing the CPL in the USA goes, it's not essential. It's useful because your JAA CPL reduces to 'training as required', but generally speaking you're looking at 5-10h including test. You need an FAA licence (Private or Commercial) before you get an FAA IR. I ended up doing the FAA commercial, because with the number of hours I had, it would be the same training, and the same test- but with a different outcome at the end!
I did my FAA IR in 10h sim, 13.9h BE76. Did my JAR conversion in 9.3h sim, 15.7 BE76. The biggest hurdle for me during the conversion was learning how to fly routes and negotiate airways clearances etc. But, in the words of the JAA examiner: "hmmm, guess you nailed that one then". I owe it to good training at Riverside and good training at BCFT. The quality of the training at Riverside is partly due to Yuri, the CFI there, who makes sure that the instructors instruct to JAA standards as well as FAA standards. Yuri is a Brit, who used to be CFI for commercial training at Stapleford (who also have a good reputation).
As for Tulsa being a boring town... yep, it's not exactly South Beach, Miami or Daytona Beach during Spring Break, but there ARE clubs and bars there, and they're pretty good (this coming from someone who did FAR too much going out during groundschool in Bournemouth and flight training in Tulsa). To the point where if I could have night out in Bournemouth or a night out in Tulsa, I'd chose Tulsa.... It's possible to get very distracted there! I had a bloody good time, the instruction was top quality, and in 4 weeks I got an FAA Multi Engine CPL and an IR.