There is the opinion expressed that gwersi would be a 'cringeworthy" mistake and Gwersi is the correct plural of Gwers.
Unfortunately the opinion does not carry further proof.
Can this be confirmed by a Welsh speaker here?
Thank you very much in advance!
gwersi is a cringeworthy inaccuracy used mistakenly by the Order of Bards Ovates and Druids (OBOD) instead of the correct Welsh word Gwersi, meaning lessons. The Welsh Language Society have confirmed that the correct spelling and pronunciation is Gwersi, and that gwersi as a word does not and has never existed in Welsh. OBOD produce a distance learning course, which they call the gwersi (aargh!), in the form of booklets and CD's. Through the use of these lessons, druids may learn about their traditions and progress on their spiritual path through the grades of Bard, Ovate and finally Druid.
source: http://wiki.answers.com/Q/What_is_the_m ... ord_Gwersu