The GARDENA gardening expert
Dear Mr. K., you have done everything correctly, and your method of planting different types of bulb in layers over each other in the so-called “lasagne” method is a good one, through which you will experience a sequential firework of colours in spring. As far as the frost is concerned, a brief cold shock is required to prepare the plants for the coming of spring in the so-called vernalisation for budding and for blossoming.
However, the cold weather we have now is quite sufficient to provide this effect. Simply leave the containers with the bulbs outside. It is too hot for them inside. Ensure that the earth remains damp enough, but not too moist. Only if the weather were to get very cold again should you place the plants in a protected area, for example in an unheated shed, or cover them with fleece.
This doesn't protect them against low temperatures, but palpably insulates them against severe temperature fluctuations. Apart from this, a temperature range of minus five or six degrees does not affect the bulbs.