Replies appreciated and they help to clarify some things.
I've checked the lens off the camera and the aperture works nicely. However, in so doing, I've realised the impact of the M or A settings. Had it set to A (not sure if it's been like all the time, but likely for some photos) and in this setting the aperture doesn't stop down but stays wide open. I'd got it into my head that it was the other way round. So, certainly for some shots, I've likely not been getting the depth of field I was after.
Still doesn't fully explain, though, as even when I've seen through the view finder that my subject is in focus and using a fast shutter speed. I'm getting blur. And that's confusing me. As it is wysiwyg, I should be getting what I'm seeing ie a sharp-ish subject.
few photos attached (not sure how they'll look after uploading):
1. showing close up focus on bamboo leaf which is fairly sharp and ok. Close up shots such as portraits seem to fare ok.
2. rope across pond - here what seems in focus is closest to me (follow rope toward shooting position) whereas I was focusing on the first post and rope there
3 pub across from memorial - I was focusing on the building and, if I remember rightly, focus peaking showed it well in focus along with the brick memorial closer to me. I know there's flare as it was bright and no lens hood, but I expected sharper on the pub and the memorial seems slightly better in focus.
It's got me wondering if the problem is human error - me. My eyesight isn't brilliant, but I've done a lot better with other lenses and it's usually not too bad for me to focus a manual lens using the viewfinder. I'll carry on some meaningful experimentation, but, so far, I'm inclined to use the lens just for closer subject matter unless there is a solution, should it be the lens that's not performing properly. (Still doesn't explain how I can see a clear focus on distant subjects, but not get it after taking.)
thanks