The seasonal nature of Metellina mengei and segmentata records is only a pointer (and true in majority if cases) but not definitive.

If the Metellina was photographed recently, it is much more likely to be Metellina segmentata than M. mengei. ID based on ventral leg hairs on metatarsi & tarsi of first pair of legs only applies to mature males … & yours is not an adult male.
Bottom right is a Noble False Widow (Steatoda nobilis)

Yes, very much🤞 Our experience of trying to relocate some of our our most threatened spider species in the much more tractable habitat of GB suggests that you shouldn't give up for many decades!

Yep, endlessly!

Superb picture, thank you, James - Wackynaerias they certainly are! Apparently the headgear is associated with secretory glands that produce a nuptial gift that increases brood size when ingested.

This is the very smart Steatoda triangulosa. It has a pretty global distribution, including the Americas. It's native to Europe but here in GB it's a relatively recent colonist.

Superb (of course!), Alan.

Excellent find and new hectad record (presumably?), James!