Thanks Paul - I very much appreciate your always pertinent and helpful comments.
Attributing makers and dates to such items is a struggle. if only they had put hallmarks on them, as in silver, but I guess I'm not the first to make that observation.
I like the shape of this one, somewhat different from others I have seen, and I thought that might be an indicator for an earlier date attribution, but I don't know enough, by far, to go out on a limb proposing such a conclusion.
Using Wilkinson as my guide, I thought the foot was a fairly good match for Fig. 1 (4,5) which he dates as 1730 to 1780. He also says that "the shearing mark, to a greater or less degree, is on every handmade drinking glass made in England before 1830. Should no mark be visible it has either had the top trimmed to remove a chip, or has been made after 1830, when the wooden end tool or woods had superseded the steel tool or pucelas".
This all suggested to me a possible pre-1830 date - but that's a shot in the dark.
Hopefully, I'll post another couple of different examples over the weekend.