A few more 1970s boating pics

We've realised that the dates on the back of the photos in my parents' album are probably wrong. Our first canal holiday, we think, was not in 1978 but 1975, making me 17 at the time, not 20.

David would have been 12.

I can't remember my father looking like this.

David seems to have spent a lot of time on top of the boat.

Two questions. Can anyone identify the Wyvern boat? The location of the two bridges? It's on the GU between Linslade and Weedon Bec (probably). I don't know the answers.