Must there be a mid-air collision in the UK in IMC in order to form the basis for establishing Class E airspace?
No, we could perceive a theoretical risk, ignore 50 years of evidence as to the level of risk,
put in place expensive measures to mitigate the insignificant risk and then look on while safety suffered in other areas because we had wasted resources. But I doubt we'd get a good grade in a modern safety management course for doing so.
There must be reasons in Germany, France, USA, etc. for doing so. Presumably there have been mid-air collisions as well.
Indeed, the idea that you need ATC in IMC but don't need it in VMC is extremely seductive. It assumes the efficacy of see-and-avoid as an effective mechanism of collision avoidance in VMC. And in the 1950s, when the airspace systems in various states were devised, it was probably more easily justified. And it's hard to break those old orthodoxies, isn't it?
This is about adopting international best procedures and practices.
Indeed it is. :-)
Or do you just sit and wait until there is a mid-air in IMC and then look at the problem again?
And how many mid-air collisions in class E in VMC in other states do I watch in the mean time?