I didn't get a definitive answer but it was likely that as I started to become more active again I had strained something around an incision site, as suggested by Peter 2016. In my follow up calls with the physio she explained that the surgery does necessitate a lot of disturbance to one's insides which is why it's important to take things easy for up to 12 weeks. Anyway, my pains did go away and now after 6 months I feel fully recovered though occasionally still get a few niggly pains in the abdomen area. Best wishes, Tony.