Magic...! Thanks, both of you, for your swift replies. Apologies for the picture quality, my camera doesn't really do small things very well.
Having now researched a little further, the shape / construction of Zygiella x-notata's web would seem to correspond with the one I saw, complete with hidey-hole and signalling strand.
Would you happen to know if Zygiella x-notata is parsitised by anything? I did witness another nearby Z-x-n receiving a visit from what I think was probably an Ichneumon of some kind, which seemed immune to the stickiness of the web and actively sought out the spider in its retreat. The spider managed to avoid any great peril and the Ichneumon moved on, however I am eager to find out anything I can about this. I do have video footage of the sequence, not sure if it can be posted here...?
Any information gratefully received.
Best regards, Nik.