Actual Cost to buy and install a boiler?

Hi Guys

We’re looking to buy a new boiler for our home but Im struggling to understand the cost of a new boiler

I understand there is the cost of buying the actual boiler and then there is the cost of installing it.

I am getting all sorts of different quotes for buying and installing.

There are companies like British Gas who do both purchasing and installing is this cheaper?

I have looked online and found various websites such as http://www.boilersprices.co.uk/ - they give an idea of prices but only give rough idea of installation costs.

Can anyone help?

Thanks
Jack