I have no problem in demonstating my IR skills in a BFR and in fact this has previously been incorporated into the BFR when the instructor knows I hold an IR and intend to do a bit of touring. As EA points out its all down to common sense and if you are comfortable that the flight you are about to undertake is within your limits - if it is not then prehaps you need to visit an instructor for a couple of hours. I also undertake a full IPC every 2 years if I need one or not.
The other point in favour of demonstrating your instrument skills in a BFR or IPC is that you are not forking out thousands to line the pocket of a JAA Examiner and the flight school. A BFR normally lasts 1-1.5 hours at normal rates, an IPC will set you back 3-4 hours at, again, normal instructor rates. NOTE : An FAA examiner (and therefore a JAA exmainer if this option was adopted in the UK), not required!
The JAA IR is not only expensive to obtain but expensive to keep.