Go to Wayback Machine run by Internet Archive
https://archive.org/web/Type in, or copy and paste in the box the original site's URL "Enter a URL or words relating to a site's home page"
http://www.familyhistorynorthants.co.uk/index.htmlClick browse history (or press return key after entering URL in the box)
Next the annual bar chart appears across the page indicating this site has been crawled and saved 52 times by the Wayback Machine between 2012 and 2019 (the year before Alan said he was closing it in 2020).
Scroll down the page to the 2019 annual calendar and click on a highlighted day of 29 December and you should get what is known as a snapshot "December 29, 2019" "1 snapshot" and highlighted in blue is a link "15:55:08" ... click the numbers and you get a new Internet Archive address to the website saved on that date.
https://web.archive.org/web/20191004233746/http://www.familyhistorynorthants.co.uk/I don't make purchases from a saved website.
Mark
Thanks Boo, sorry I missed your direct link to webarchive. Hopefully the instructions might be useful for others to find other now defunct websites.
I went to the British Library
https://www.bl.uk/collection-guides/uk-web-archive, and then to the UK web archive website of old websites, but couldn't get a return for the site.