A broker will assess your circumstances and should be able to tell you in advance which lender has the best tracker rate for you. So you only have to apply to the one lender. But make sure you know which lenders the broker is acting for as some brokers only deal with a limited number of lenders while others have a wider range. Ask. Few if any brokers deal with National Irish Bank, by the way, because National Irish Bank choose to only distribute their mortgages through their branches. So if you want to be sure you're getting the best deal you will have to approach a good broker and National Irish Bank to see who comes up with the best rates.