I would put the pots in the greenhouse to prevent freezing. Terracotta has a tendency to crack with the freeze and thaw cycle.

are they frost proof terracotta? some pots are ok down to -5c. if not then in a greenhouse/coldframe, unheated porch.

Besides the concern for the pots, the bulbs themselves shoudn't freeze. Better in a cold greenhouse.

Thanks I will pop them in the greenhouse. Might be safer anyway as I think I have a hedgehog checking my work every night now down at the bottom of the garden!!!
Thanks all.

Since we don't have hedgehogs here in the States, my ignorance is boundless. I thought hedgehogs only ate bugs, worms, slugs, and the like?

We don't have hedgehogs here either, but we have raccoons, possums & skunks. The squirrels will dig up the tulip bulbs for a tasty snack, and they'll leave most of the acorns they stashed away so in the spring, my garden becomes the land of a thousand oaks. It happens every year!

I wonder if your nocturnal 'checker' is a squirrel or a fox. Hedgehogs don't normally disturb pots in my experience.