For commercial weight stuff, if you need a one-off recovery it is generally pretty costly. The trouble is it has to be a fast response so a friendly plant mover may not be able to just drop a job he's on and get there quick. And if you are obstructing a highway, unless you can convince the Police you have someone on the way, they may call a commercial recovery firm on your behalf and you have to pay!
Several companies (saw one on ebay yesterday, and there is the Roadsure scheme) offer a commercial weight recovery insurance service for £70 and up as a 12 month insurance policy.
For one vehicle I'd be tempted to play safe and take out a policy. But it would be good to know of recovery operators in various regions who are sympathetic to our hobby and who charge accordingly.