Filling out CN23 for shipping a box from Sweden to Northern Ireland.

The box is for myself as I am planning a longer trip trtho Noern Ireland, and might eventually be moving there. It mostly contains my clothes, and some mugs and drinking glasses. I am not sure what export category to label it as, since it is a box for myself. And when filling it the value of the items I am a bit unsure as well since it is old clothes that I don't know what they cost, but also wouldn't be worth as much today. If I understood correctly I will need to pay VAT if the total value is over £135, but I will not need to pay customs duty since it is being sent from the EU to Northern Ireland.

Hi Isak Axelsson,
Please contact our Customs and International Trade Team as below:
Imports and exports: general enquiries
Thank you.