However,that was not the average price from multiple retailers though,as even Amazon and Ebuyer does special offers at times and so does Aria. The cheapest I have seen recently is £161 recently from Aria on a limited time offer. My mate even got a pre-overclocked HD7770 for £65 on a one day special from Amazon and it was £25 cheaper than any other place.
None of the other CPUs outside the K series have shown this though,so sadly I doubt its down to currency changes only.
For instance the Core i3 CPUs have stayed at between £90 to £100 since 2011. Pentium dual cores and low end Core i5 prices have either stayed stable or decreased. The T and S series Core i5 CPUs have dropped in price with IB. The socket 2011 CPUs have actually stayed stable or decreased in priced.
So,you need to consider the other CPUs too. Fluctuations should also affect these CPUs too,so a Core i3 should be £100 to £110 now for example,or a Celeron G530 or G540 should be £40 now,not £35.
The AMD CPUs have stayed stable in price too,and AFAIK AMD has not reduced the RRP for most of its CPUs for ages and they are in USD.
The only ones which they reduced the RRP of in the last few months was the AMD A4 CPUs.