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Placing a canonical tag on a webpage that points to a different URL is a suggestion to Google that the page is the same or extremely similar to the page at the specified URL.  It is a suggestion that Google might or might not honor. The more similar the pages the more likely Google is to honor the canonical instructions.  If the pages are not substantially similar, Google will likely ignore the canonical. Your example pages are very different so Google is likely ignoring the canonical instructions. When Google and other search engines first decided to use canonical tags they were not very picky with how people used them.  More recently Google has become more picky and is ignoring lots of canonicals and even ignoring canonicals that they use to honor.

Thanks Roman, I will begin using the on page grader for our local pages.

Just realised, it's most likely a post not a page e.g: https://www.padstowsealifesafaris.co.uk/endangered-sea-life-uk/ (blog post with date stamp) https://www.padstowsealifesafaris.co.uk/boat-trips/ (page with no date stamp.)

Do all of the pages have the same title tag? That is usually what is meant by cannibalization.

Use if it truly is a point of emphasis in the context of the copy. Another reason not to do it has been mentioned in several recent posts.....It gives away the keywords you are trying to optimize to your competitors if you are too obvious.