To be honest @crlhrrs I’ve never paid energy bills (or any bills actually) bi-monthly. But I’m a straw poll of one! I would imagine it’s pretty unusual though. I’d be surprised if SSE weren’t OK with moving to monthly. I had a look for you and they do offer monthly payment options as well as bi-monthly so you could give them a call to see if you’d rather not have the big bill every 2 months?
https://www.sseairtricity.com/ie/home/help-centre/contact-us