Rustle,
In the States, to get FAA IR (assuming you have reasonable flying experience/confidence) takes 3-4 weeks, written & oral test, then flight test. Approx. 40 hours of dual time in total. It also counts as IMC on return to UK. Cost? Less than $5,000 I should think.
Last time I checked in the UK (admittedly about a year ago), because of the new JAA changes to IR qualification/training, only a couple of schools were offering IR in the UK, I was quoted approx. 9 months elapsed, and substantially more than $5,000. Things may have settled down since - but what I meant by "hopeless" is that the UK qualification is inordinately expensive & time-consuming, for no apparent benefit over the US qualification.
If I am out of date - please let me know!