Fainted after getting out of bed at Chywidn. Banged head and back of body. Intermittent symptoms of concussion (thumping head, out of sorts etc) for severals days afterwards. Sore neck like mild whiplash didn't last too long. Spasms/pains in buttocks (esp left) and really tight hamstrings lasted longer.
I think it was a case of low blood pressure, warm bedroom, slightly dehydrated (after long run) and just got out of bed too quickly. GP tests all normal except for iron, which was borderline low (as expected). Saw physio after 13 days for persistent tight hamstrings/sacroilliac joint. Good progress by second physio visit (having stretched twice a day) and then another week before I felt normal.