Pearlwort? Spurrey? something else?

Pearlwort? Spurrey? something else?

Observation - Pearlwort? Spurrey? something else? - UK and Ireland. Description: Prostrate plant growing in roadside gutter in housing estate. Differs from the usual urban pearlworts (procumbens/apetala/filicaulis) in having easily visible petals (the named species have absent or diminutive petals), and does

Prostrate plant growing in roadside gutter in housing estate. Differs from the usual urban pearlworts (procumbens/apetala/filicaulis) in having easily visible petals (the named species have absent or diminutive petals), and doesn't appear to be rooting at nodes. Some of the flowers have a pinkish tinge, but this is washed out in the photograph.

Doesn't appear to match Sagina nodosa or Sagina subulata, and is more compact than I would expect for a Spegularia.

[Updated 17/8/13: various things appear to have gone wrong with the initial entry of this observation.]

[Updated 20/8/13: photographs replaced; location fixed.

The petals are very pale pink, looking white in most lights.

The calyx is tubular and less that half the length of the petals. This, I believe, eliminates Sagina, Spergula and Spergularia.]

[Updated 03/10/13: I found (back on 21Sep2013) a second plant 95m away.]