Would piss me off, but I would just be glad to get it tbh. I would have a moan on twatter about it after though.
We had something similar happen last year... We were awaiting a new bed, and the time slot was between 4pm and 10pm. So we held off having dinner, and waited, and waited, and waited.. six hours! Rang the helpline at 9-ish to check they were still coming, and got no answer. It just rang and rang.
Half nine came. The delivery driver rang us and said he should be here within the hour. Half ten came, then eleven. We were verrrrrrrrrrry pissed off now!
11.45pm, we got a text from the driver ... 'unfortunately, I am unable to make it tonight with your goods, but shall endeavour to deliver it between 8 and 12 tomorrow morning.'
I was livid, and tried ringing back, as there would be no-one in the next morning.
He didn't answer, obviously. 
I texted back saying we would not be in. No reply. We had a big fat card through the door though saying 'tried to deliver your goods at 11.40am.'
I was so mad that I cancelled the order and told them to shove the bed.
2 MONTHS it took to get a refund. I will use Argos next time!