Its the 200 hours under IFR to qualify for the IRI course. The UK has never logged time IFR, only time by sole reference to instruments i.e. actual time flying on instruments as opposed to flying IFR in VMC. Consequently, the UK equated 50 hours by sole reference to equal 200 hours in accordance with IFR.
Full UK FIs traditionally were qualified to teach instrument flying, fewer have qualified since JARs came along because it was neither mandatory no cost effective for many, now it will be even less cost effective so the numbers will diminish rapidly.
No its not a change from JAR, merely a change in the way JARs have been applied.