Help booking a blood test in James’s?

My GP is in Lucan but I work near James’s so I asked my new GP if she could give me a form to get my bloods done in James’s.
She was adamant that there was no form and all I needed was a letter from her saying what they needed to test for.

I’ve been trying to book it online but am not sure if I’m looking in the right place.

There’s “St James Hospital - GP Referrals” and also “St James Hospital Outpatients Blood Test Department”.
I don’t think my GP actually referred me, she just gave me a letter and said to go to whatever lab I wanted.

Can anyone link me the correct page? Sorry am just a bit confused about the whole thing now.