Lapsang would probably be a time-appropriate tea, but I would be hesitant to serve it for a Jane Austen gathering. It's a bit too, er, masculine.
Since the earliest reports of a native tea in Assam date just at 1815, it's pretty safe to assume that the only tea Jane Austen would have been acquainted with is Chinese tea, so cross anything Indian or Sri Lankan off the list. I would also go on a limb and say that Jane would have only known Chinese black tea--it was what the Chinese primarily traded and it had a better chance of holding up through the voyage around Africa than green.
Most references you'll find to tea around 1800 call it Bohea, but that's not really Bohea as we know it today. Back then in Western parlance, it really was a catch-all term for tea. I think that today, black teas from the southeast of China would most closely fit the profile of the general selection available to the early nineteenth century English upper middle class.
From Adagio's selection, I'd likely choose their Golden Monkey
. It is a Fujian black that really does have a wonderfully full flavor, and it is quite cost-effective if you buy it in larger amounts. If you'd like to offer a black, oolong, and a green, I'd suggest adding a Wuyi oolong
and a longjing (dragonwell) green
. Oolong really wasn't a known thing back in the Regency days, but it would be a nice thing to offer a modern crowd. Longjing, too, is a bit of a stretch. It's not really what Jane's crowd would have had if they were able to try a green, but it's not entirely off the mark and it is what modern drinkers expect out of a Chinese green.
I wouldn't try to blend them all together because--without a lot of care--you'll just get a bitter, undrinkable mess. In my experience, greens do not work and play well with others.
If you would like teas that are actually called 'bohea
' and 'hyson
,' Upton Tea Imports sells a couple reasonably priced Chinese varieties by that name.
As far as adding milk, lemon, or sugar...I've hosted a lot of shindigs in my time, and outside of my stint as my college sorority's Mistress of Etiquette, I've found that it's just better to overlook slight gaffes. Make all three available to whoever wants them, whether the tea calls for it or not.