As of Aug. 19th, 2014, UK postage is not expected to increase in the near future. It already increased in 2014 after holding steady for two years since the prior increase. UK postage rates increased on March 31st, 2014.
The increase was 2 pence for first class stamps, from 60 pence to 62 pence; and 3 pence for second class stamps, from 50 pence to 53 pence. Royal Mail states that their postage rates are still "amongst the best value for money in Europe," and that the average across France, Spain, Germany and Italy is 67 pence for first class letters.