We've been, like everyone else, walking more than usual. Today we walked a new route. The path was really tricky to SD on having to stop and go up against barbed fences to let people pass. We were wedged between a group carrying a pushchair down to a beauty spot (we didn't realise until we got there the insistence to go down the very steep rocky stepped path was because they were clearly gathering for a day out with other families as we saw approx. 20 people in groups in a clearing!). At one point we stopped so we didn't get too close to people in front and a family group behind us went past and I felt their presence on my back, you know that little brush against you! Then there was a group of 3 in their early twenties ish with one man coughing and sensed them very close behind so moved over to let them past. On both occasions a polite 'excuse me' would have been better so we could suitable SD as best we could.
We sat on a hill near a gate, we could see everyone going through it opened it with their hands. My DH and son used their feet to knock the catches open so we didn't have to touch the gate. If we have to touch a stiff gate, we instantly use our hand spray gel, I'm so glad we didn't need to do that today!
I watched as kids climbed over the gate, people opened the gate then rubbed their face or opened a drinks bottle or ran their hands through their hair! I estimated that in the 10 minutes we sat there, approx 20 people touched that gate and not one used a handgel or wipe etc afterwards.
It's not exact, but that would be 120 people in an hour and over a 10 hour day of a busy area, approx 1200 touching that one gate. Statisticly, some of them would be carrying Covid! 
These will be the people who get Covid and say 'well I've only been to the Supermarket and out walking'!
I don't think I'm being overly cautious? I feel safe outside if we SD but I try to imagine every person and every surface could be carrying Covid to keep risks to a minimum.