Links within page keep bringing error page

Hi,
We have a local support groups page on our site
https://www.grandparentsplus.org.uk/local-support-groups the links within the page keep adding our domain in front of the link address ie: instead of going directly to https://www.grandparentsasparents.org.uk it links to https://www.grandparentsplus.org.uk/www.grandparentsasparents, which of course brings it back to our site which does not recognise page.

It does not do to all the links, but it does on most of them. The email links work fine, just web links. Everything is linked correctly – there’s no mistake in the addresses etc.
Your help/advice would be much appreciated.
Many thanks, Kind Regards
Sacha