The Allied Irish Bank offers both business and personal accounts for UK customers. You need to create an account with the bank first and register at Allied Irish Bank online in order to access their online banking facilities. If you have an account with the bank and have the AIB login details, then the process is pretty simple as explained below.
Click Here to reach the AIB Login Page.
Below are clear noteworthy instructions you can follow to access AIB internet banking.
How to Log into the Allied Irish bank online Net Banking account?
If you already have registered with internet banking, the process is unambiguous and will take minutes to get done. Click on the link above and you will land on AIB homepage as shown below.

Choose Online Banking from the drop-down menu that appears as you place your cursor on LOGIN, which is placed on the top right corner of the page.

You will be redirected to their online banking page. Click on Online Banking Login button which will redirect you to the AIB online banking Log in page.

You will be prompted to enter your customer ID and Password. Once you submit the right credentials, you will be logged in to your online banking account.
If you have a business account you wish to access through online banking, then go back to the Homepage and follow the same procedure. You just need to select iBusiness Banking from the LOGIN menu.

You will be redirected to their Business Banking page as shown above. Select Log on to iBB Button, which will redirect you to the login page.

The AIB iBB Login page will ask you to fill in your details. The interface will verify your credentials, letting you access your online corporate banking account.
First-Time Users and Enrollment for AIB Online Banking AIB Internet Banking | AIB Login for First-time user
You can log in to your internet banking account only if you have registered to access it. Click on the image below which will take you to their online banking page as shown here.

Select the Application form to download it. Please complete the internet banking registration form by filling in the needed details and submit it to get your online banking activated.
AIB Internet Banking Information
Branch Locations: Branch Locator
AIB Website: Bank Website
Customer Care Number: +44 (0)345 600 5204
Also, if you are looking for help with other banks in the UK, here is a list of all banks in the UK.