Well, folks, I am feeling fairly normal again (well, normality's all relative, ain't it!

) now - a week+ since my arachnid encounter.
The anti-toxins and other things the medics pumped into me were probably responsible - at least in part - for my recovery, but at the same time responsible for the lingering nature of my unwellness. I feel a tad toxed-out and medically poisoned (such is the nature of medicines and healing).
Henceforth I shall approach unknown dark corners of sheds and their contents only after having fumigated everything with enough Mortein-type products as necessary - plus 50% extra for good measure.
Might also invest in some long sleeves and long gloves; the gardening gloves I commonly wear on such excursions are probably as much a risk as none, because they could allow nasties to get inside, be trapped, and take their revenge.
I returned to the scene of the incident today and, after having bombed it thoroughly, took a good look - to discover a veritable condominium of webs that conformed to those in my red-back reference pics.
Also found the sills of Crusty to be full of such webs, so I blasted a whole can of arachnicide through the access holes along the tops of each sill, then double-bombed both my storage sheds for good measure. If anything survives in that environment it will be a miracle. (Of course, I daren't go in there myself now for a couple of days lest I also expire from the poisons!)