mcgrattan, If you are looking for a dependable lab try MetrColourLab in Birmingham. You can find their page with prices etc., on the net. There is Transpacolour in Leicester. I have used MetroColour for 35mm slides and prints; and also med. format slides and prints. Used them for several years now.You can post off film and results can be back in 3-4 days. Have also used Transpacolour in the past, and they too were good. Peak Imaging have always had excellent reviews, but I have never used them as they are pricier than a lot of the labs.
Best of luck.