Hi,
As these purchases won’t be imported, they are completely outside the scope of the UK VAT system.
I don’t use Sage, but have found a list of standard codes here: https://gb-kb.sage.com/portal/app/portlets/results/viewsolution.jsp?solutionid=200427112155761&hypermediatext=null. T9 seems to be the most appropriate, you would then need to record the full amount (including the Irish VAT) in a net column. I think that T1 might wrongly imply that you had received the supply of goods in the UK.
The Irish Revenue has guidance on reclaiming VAT here: https://www.revenue.ie/en/vat/repayments-to-unregistered-persons/foreign-traders-and-vat/foreign-traders-established-outside-the-eu-paying-irish-vat.aspx , but the list of items where VAT is not recoverable (as shown in the notes to the claim form) probably covers most of what you’ve bought!