Of course, the cost of your public liability insurance will depend entirely on the nature of your business and the risk that an insurer believes to exist for damage or injury to third parties, the amount of cover you actually need and so on.
So - without knowing all the details and having an insurance price calculator to hand, it's impossible to give a simple answer to the question "How much is public liability insurance". However... here's a graph that might help you research a little further:
In surveying Quotiva customers we discovered that the majority are paying up to £250 per year for their public liability insurance, with around 20% forking out £250-£500 and a small minority of businesses needing to spend over £1000 p.a. for PL cover.
As you would expect, business insurance cost changes too depending on the company type. A sole trader public liability insurance policy is more likely to cost less than £1000 per year than PL for a limited company for example. In fact, over three quarters of people we surveyed looking for self employed public liability insurance were paying £250 or less per year for their premiums.
In summary - get a public liability insurance quote comparison using our single page form, be honest and realistic in your cover requirements and get quotes from a number of insurers on a like for like basis.
Source quotiva.co.uk data 2011.