Dia daoibh a chairde -
A note of caution here with the Pimsleur offer. If you do order, make sure that you uncheck the box below the Submit button. Else, you will automatically receive, otherwise unsolicited, the first chunk of an expanded course at a cost of hundreds of dollars. I learned the hard way - cost me about $20 to return an unwanted course.
I'm not sure what you would get as a follow-on with Irish - maybe nothing (don't think they have the usual 45 hours of instruction for Irish). I have the old 4 CD set. I really like the Pimsleur method (used it for other languages) - but you have to adjust for Munster dialect (not just pronunciation, but many words different from what your Ulster Irish experience would be). One other thing - there is a transcript of the CDs on the internet (Pimsleur uses little or no printed material in their method.
There is quite a bit of Pimsleur Irish on YouTube - so you could check it out before buying.
Tóg go bog é,
Seanduine