Below we have is a extensive list of driving instructor insurance brokers in the UK, which offer insurance specifically for driving schools and driving instructors.
We advise you get many quotation as possible and make a best decision that will be affordable and meets your needs as a driving Instructor. 

Some of the things you might want to consider when obtaining quotations are:

• What specifically does the policy cover?
• What is the excess on the policy?
• What is the excess for windscreen damage?
• Is a replacement vehicle provided in the event of a fault and non-fault claim?
• For how long will the replacement vehicle be provided (is there a maximum time period)?
• If you are hit by an uninsured driver, how will this be recorded on your policy (i.e. as a fault or non-fault claim)?
• If you provide off-road tuition to drivers under 17, make sure you ask for specific details of cover for this element.
• If you have family or friends under the age of 25 that are likely to be driving the car for social, domestic or pleasure, make sure they are covered, too.
• If you provide instructor training, is cover provided for this?
• Does the premium offer no claims discount protection?
• Is there any additional charge for paying in installments?