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I think it is Veronica persica, unfortunately the image has gone a bit yellow so the leaves and flower colour is not quite right but the flowers were bluish not purplish and leaves very much unstalked.
Notice that the pedicels are easily more than twice the length of the leaves. This is the key difference in Stace 3rd ed. Also, notice that there is no sign of a fruit where the flower has fallen. V. persica rapidly makes a capsule, while V. filiformis only rarely does.
Lat/Lng: 54.368, -5.58297
OS grid ref: NW673028