Search function

I am not really sure what do you mean?

I basically want to create a search box for the items at https://lovefamilyholidays.co.uk/best-holiday-destinations-family-breaks/
to display on my homepage.

Would that be possible?

Thanks

Yes it is possible, you can use either [adverts_list] shortcode for this with params show_results = 0 and redirect_to set to main page with [adverts_list] shortcode https://wpadverts.com/documentation/creating-ads-list-adverts_list/

As an alternative you can use simple HTML for to do that

<form action="https://example.com/link/to/your/main/ads/page" method="get">
<input type="text" name="query" id="query" placeholder="Keyword ..." />
<input type="text" name="location" id="location" placeholder="Location ..." />
<input type="submit" value="Search" />
</form>