Thanks cinnamon ... the left one rubs at the back, where the top of the shoe touches my leg, and I have a blister there. Also, for some reason, on both feet my big toe rubs against the next toe, and I have a blister at the tip of the second toe on the right foot. Have experimented with looser vs tighter lacing. Terrain was tarmac, but country roads so parts of the tarmac not that well-maintained, and it was dry. Almost feels as if the shoes don't fit properly, which is annoying because I had a gait analysis and proper fitting and advice, and tried them out on the treadmill in the shop before buying - although admittedly only for a minute, which doesn't compare to a full outing. Will take them back to the shop tomorrow and see what they say ... I have 30 days to decide whether to exchange them but they have a sale on at the moment so don't want to risk not being able to exchange for something affordable (I have to pay the difference if I exchange for something more expensive).
Annoying .. I chose the Brooks Glycerin partly because they seemed comfortable and partly because they were such a good deal (half price at £60). I also really liked Saucony Ride 6, but they were £80 (reduced from £100). Should probably have gone for those!