Thanks Velocivixen and DebW. I've relubed all the pivot points on the derailleur as lph suggested and the shifting has already improved, but it's still sticking a bit. I haven't checked the cable housing yet but will do that in the next day or two when I have time to remove the bar tape etc. I think you're all right about the cable/housing. Probably time to change it or at least clean it out. DebW, it didn't occur to me to lube the shifter. Thanks for that.