Thanks Kestevan, all sorted now.It's worth checking the how clean the cable cut is under the ferule, if its not perfectly straight and clean it can cause the inner to rub/catch. I found cutting the outer with a piece of inner cable in place helps to stop the outer deforming (and use proper, decent cable cutters, not pliers etc).
Having said that, I had a poor experience with Lifeline cable outers on SRAM. No problem with them on Shimano, but was never happy with the shift quality on my SRAM Rival setup.