Thanks to Tim, Maggie and Allegra for their suggestions here and on the board. I'd understood that it wasn't possible to book tickets online for disabled access, and the venue had just referred me back to TM, but about an hour after I posted here and on the boards, 
TM.ie got back to me. They said the phoneline (same # I'd been trying at the beginning) had been working fine all day, and oddly enough I found that it worked immediately after that. So I've got my tickets booked, thank God!
<br><br>Angeline<br>