well, what do I know then

As a type of product, these things can vary enormously in shape and decoration from their beginnings in the latter part of the C17 to as recently as early C20. Regret I don't have Mary Boydell's book, but my opinion on the horizontal cuts indicating the likelihood of an Irish origin in particular, isn't something that I'm aware of - there are other forms of decoration that are more widely and better known from that country, but.............. who knows, and Ms. Boydell was doubtless vastly better informed than me. (I have Westropp's book, and Warren's - does the lady's book cover additional Irish material??)
For my money - when comparing with Irish glass - this piece lacks the density of cutting for the period you suggest Mike - but the Irish were being clobbered with the Glass Excise Tax from 1825, so perhaps this changed things.
Folk bang on about the Regency as though it lasted an eternity, whereas it was over in a matter of nine years when our dissolute Hanoverian descended monarch became George IV in 1820 and serious collectors tend to loose interest after his demise.
If you take the type of star cut as indicating c. 1830 then you could I suppose hang your hat on that alone and flog it as such and it would be a rash person indeed who contradicted you, unless they were especially clever at dating jellies. Call it a date you consider your research indicates, and if anyone contradicts you, ask them to explain why.

We're back to the problem of lacking a good book on these things - I've looked in Therle Hughes small and rather limited booklet but there's nothing there that comes close to yours, and the Delomosne catalogue for the Tim Udall collection is in a different world altogether - concentrating on the high spots of C18 pieces only. In the past collectors have concentrated on the C18 and it's images of those that have made it into the books, leaving us a lot less informed about the C19 pieces.
There's no help in Bickerton either.
As for the dating of the set of jellies in your link, my opinion is that it's possible that different people might have different ideas. Sorry this has not really been of help. Maybe it's this apparent difficulty of dating that stops others from commenting - mind you who wants to go out with a jelly.
