I had a feeling the Parliament also had a mini-session before Christmas, but I could be wrong- I'll have to chase that one up.
Jane Bennet is in London essentially from New Year's until early May. However, apart from viting Caroline Bingley once, and having the visit returned two weeks later, she doesn't seem to do anything in particular, and it's hard to tell whether she was involved in any of the "season" activities. She has been to London before (presumably staying with the Gardiners) but again, we don't know what she did, except that one young man wrote some verses in her honour.
Caroline and co. leave Meryton at the end of November and move to London "for six months", they could be involved in the Season too, but it's impossible to be sure, since we don't know what they did, really.
Details of who did what and when in P&P have been worked out by Ellen Moody, nad you can find her calendar HERE