Hi Heather!
Nice of you to mention this disc which I enjoy very much too. I think the music is absolutely charming, and the playing is excellent too! I'd never have guessed anyone on GMG had this!
The Olympia CD was a rerelease of an older Polish LP which has been put on CD once again in 2000 (perhaps there were other times too, I don't know). So I have it under a completely different (and pretty unenticing) cover:

Another great thing about this disc is that it costs about 4.25$ (12 PLN) - I got it almost by accident, and I have the price to thank for that.

The music is quite enjoyable to listen to, and a good variety is presented. Although the music is typical of its time, many pieces exhibit a definite Polish character and wouldn't likely be confused with music from other countries. This music is good enough that I would like to hear more of the music scene in Poland at this time; I wonder how many other recordings are available.
I think Olympia released a few more discs of this type - there was a whole series, something like "Early Polish Music", don't remember the name exactly.
Anyway, if you're interested in Polish music from the "Gurnian" period (late 18th c., early 19th c.) there's quite a lot to choose from nowadays. I'd suggest you take a look at the catalogues of the following (Polish) record companies:
PRO MUSICA CAMERATA - this is a label associated with the Warsaw Chamber Opera, and even though they specialize in Polish baroque music they do have some pieces from the classical period in their catalogue. Incidentally, I notice the prices given on the English version of their page are about twice of what you have to pay if you read Polish...
Acte Préalable - they've recorded a lot of the stuff by Franciszek Lessel and Ignacy Feliks Dobrzyński, also some Ogiński and Kurpiński. You have to be wary though - they have a strong proclivity towards mediocre performers. Some of their recordings are by first rate ensembles (like the Wilanów Quartet) but others are by some abominable second raters.
DUX is another label perhaps worth exploring. Unfortunately, the only way of exploring their catalog is by browsing
this page on the site of their official Polish distributor - the categories here are quite useless and navigation isn't easy.
For music from other periods,
Musicon is very good for early music.
CD Accord is great for late 19th century and 20th century.
And last of all, if you "do downloads", I'd like to refer you to
this post of mine. You'll find links to pieces by Janiewicz and Dobrzynski (and Lessel) there.