Susan,I doubt if Neville ever got as far as the bedroom by the time he'd finished his chores. After supper and when Jeremy had left,Neville finished off in the fields,came in,took the dogs out as was his usual routine,returned,showered,and then I suppose after a " snifter " and cigarette,retired to bed,which by my reckoning ( during harvest-time ) would be around 1am.
There'd have been no need in him going upstairs,as he showered downstairs,I suppose because the boys were staying there at the time he didn't want to disturb them with the sound of running water.
I do think that Sheila clobbered her father as he came out of the shower and from there it began. The burn marks on the back of Neville were done with minus his top on,as it didn't show burn holes in the material. I honestly think that Sheila caught her father unawares and bashed him in the bathroom, causing the shower-head to come asunder.