Still got a wound that won't heal, and a bit of poking around with tweezers located some black stitching. I pulled with all my might (think story of the enormous turnip :-) as did dh, but we could not get it out.
Finally rang the local surgery, who at times seem to exist to make sure that no one gets and medical treatment at all. . . who grudgingly gave me an evening appointment.
Saw a new (youngest there) doc who was actually quite interested in my condition (rather than looking at his watch every half minute like my previous GP did) , and who agreed that yes, there definitely was a stitch in the wound and worse, he was pretty sure it was infected.
Got the stitch out, he said it was "long term dissolvable" and doing no good at all, so might as well come out. I am now on antibiotics, hoping desperately that they work before my proposed double fill in Belgium in 8 days time. . .