I'm about to take on some freelance training work with my local council and so am re-registering as a sole trader. They have said their trainers have £10m worth of public liability insurance, which is more than I had in the past, and a lot more expensive. There don't seem to be that many insurers who offer that in my area, either. I have asked for clarification if this is essential, but does it seem excessive?
Sounds alot, I get insurance via simplybusiness, you could give them a try. You may have already done it but it may be worth asking them to tell you what they need in writing, so at least you can trust it if it's just what you're being told on the phone.