There may be a solution. If it is true that other ISP's may have space to spare in your exchange, then switching it Eircom may be a mistake. Like it or lump it, Eircom would have the biggest backing I'd imagine. This is down to trust. People will go with who they know. Eircom has been around the longest, and they are the owners of the lines. BT has a nice backing, probably due to their attractively priced packages.
Here's a possible solution. Before I migrated to BT, I was with UTV. My only reason for changing was to avail of the top package for less money. UTV were grand (as good as you're gonna get), and I'd recommend their services to anyone; for the lack of anything better. Also note that they're more expensive than BT, but still cheaper than Eircom. If you're going to change ISP's, then I'd advise you give them a go. I doubt they'd be over-subscribed down in Cork. They're one of the bigger, but lesser known companies. That's my logic for thinking they may be better for you than Eircom and BT.
UTV Clicksilver Broadband – High Speed Internet Connect
Seifer.