I'm in Belfast and in the same position. It's inexcusable. Amazon one-day delivery can get here with no problems; Royal Mail can manage it too. But UPS can't?
I plan to keep a close eye on the UPS tracker tomorrow - if it gets as far as their depot in Mallusk, it'll stay there until Monday. If that happens, you can phone and ask to pick it up. They're open till 8pm. I did it not long ago when my Macbook Air arrived in NI on a Friday afternoon, and therefore too late for delivery on the day. They were fine with it - you just phone, quote your tracking number (the long UPS one), ask them to hold it for pick up, and bring some ID with you when you go.
Other folks with a Monday scheduled delivery could probably do the same if they see the package scanned in at their local depot..