Jezd,
after this harsh Winter?
What is it that puts you under the misapprehension that a winter, like we have just had, kills bumbles?
Just not true. They hibernate safely away from the ravages of the cold winter and emerge in the spring when the weather warms sufficiently to arouse them. That is why they hibernate in north facing banks, for instance. So that the soil has to warm from generally warmer air temperatures, rather than from direct sunlight.
Their far bigger danger is that it warms too early, they all come out and are then caught by a prolonged period of very cold/wet weather which may either get them or prevent them establishing a nest.
While they are hibernating they are relatively safe. They have been doing this for millenia in much harsher conditions than we experienced this last winter. All your post does is 'unecessarily alarm' the uninformed to the wrong reasons for the bumble bee decline. Sticking to poor weather in spring and insecticides is much, much nearer the truth.
Regards, RAB