It took me ages to find a company that would provide PLI for my non-commercial workshop unit. No problem getting cover if you're running a business, but if it's purely a hobby/non-commercial workshop, most insurers aren't interested.
Googling around, I found a company called Commercial Express that offer a hobby and club policy, and I found another article that said that the policy was suitable for individuals. I gave them a call, but they only deal direct with brokers. They put me in touch with one of their brokers at http://www.insuranceprotector.co.uk/, who were actually really helpful!
The guy at Insurance Protector went back to the underwriters at Commercial Express numerous times to check they were happy with me only being a hobbyist, non-commercial entity, and even got them to change the wording on one of their standard welding clauses (a bit hard to have a designated firewatcher when you work on your own!).
In the end they arranged liability cover on their liability (per capita) policy, customised to what I wanted.
I ended up with £1m of PLI cover for £270/year.
Hope that helps!
Dan