Dual National Irish/UK middle name on passport

Hi Ask Ireland,

Hoping there might be some fellow dual nationals lurking that can help me with a query. I’m a dual national recently applied for my first British (to get a Australian visa)

However I’ve heard back from HMPO that my application is on hold as ‘The name on your document doesn’t match the name you’ve asked us to show on your British passport.’

The difference is my Irish passport omits my middle name, no idea why, does anyone know how I can resolve other than waste €75 on applying for an Irish passport I don’t need for another 7 years?