I should add there are very few scenarios where a CPL (or an ATPL) is of any value whatsoever without working in an AOC context.
The only one I can think of, off hand, is being a paid company pilot (i.e. it's in your contract that you have to fly). Some others are perhaps charity flights beyond a certain radius or something like that....
The reason for doing a CPL/IR over a PPL/IR (JAA) is that there is very little difference in the amount of junk one has to swat up, so one may as well do the CPL. Never know what grandfather privileges or whatever one might get in umpteen years' time.
With the FAA IR there is a lot less reason for a CPL. You have close to zero chance of getting UK Govt permission to do sub-airline-level commercial work in an N-reg plane (AOC or not), though the "company pilot" case probably still applies. On the other hand the FAA CPL ground school is pretty reasonable (I've just done it) so the CPL is still probably worth doing (over the PPL) just in case it gives some extra conversion privileges if/when EASA deliver on their pretty amazing public statements that they want to be able to exchange an FAA IR for a JAA IR (an essential step as part of their longer term objective of kicking out all foreign-reg planes out of the EU)...