I only froze the excess milk, or if it was a bank holiday weekend, and in Lanisoh bags. Otherwise, I pumped directly into the Avent bottles and then took those in.
Nursery had some frozen milk for emergencies, and the first couple of weeks I gave them an extra bottle the first day which they then rotated, just so that I knew that they had more than enough.
I also told them that as long as it was fresh milk, they could reheat it once as long as it hadn't been left out for more than 30 minutes (ie long enough to cool to room temp) which reduced waste when he just wanted enough milk to go to sleep then would wake up ravenous for the rest an hour later.
The thing I hated most was being away for work, and having to pump and dump when I couldn't get the milk home. It really, really irked me when the freezer stock was being depleted