If you want to use your regular bank for a mortgage, there is no reason you can't apply.
You will need to meet all the eligibility requirements and have done sufficient research to feel satisfied that your bank offers the best interest rates you're going to find.
However, a mortgage broker will often save you a significant amount of time, energy and expense by recommending specific products with niche lenders who are ideally positioned to provide the funding you need.
Help2Finance Brokers can also provide independent advice about a range of factors, such as insurances, alternative borrowing products and support schemes.