A pair on the Blind Yeo at Clevedon - male with the distinctive white flanks.
No interactions present.
Female Tufted Ducks can show a lot of white on the bill (like a Scaup). To me this bird looks like a female tufty (the dark brown colour of the back and lack of any vermiculations suggest Tufty)
Yes, both tufted ducks.
In addition to the features mentioned by David (dark brown back lack any grey vermiculations), the head shape - with a visible crest, and the relatively large amount of black at the tip of the bill confirm this is a female Tufted Duck.
Lat/Lng: 51.424707919488, -2.8696095943451
OS grid ref: ST396698