When comparing prices with suppliers always remember to look at additional charges on your invoice. Often people will see two prices side by side and although they may look similar, there are sometimes fees & charges which are not always added on until the point of invoice. Below are the theee main ones to look out for.
Some carriers will charge some or all of the above, some may charge none, and each will have a different invoice layout. For instance some will include the congestion charge within their pricing, whereas some will add it at the end of their invoices. With this in mind it is vitally important to know how your carrier charges so that you can control your costs and make like for like comparisons.