How do I put a message on my listings to potential buyers that I will be unable to post for 2 weeks

[*vyolla*]

I woudn't do that, most buyers won't see it and you'll be welcomed home to a barrage of item not received claims and late delivery defects.

See if you can use Time Away setting. You will need to use a desktop browser, not an app, to access this, and your listing must be a fixed price Buy It Now, not an Auction.

Use Time Away settings here:

https://www.ebay.co.uk/vac/TimeAway

With Time Away you have two settings - you can hide fixed price listings from search for 1 to 30 days or keep listings visible, but with a notice that you're away for 1 to 15 days.

Failing that, end your listings and then relist them when you return. They will stay in your My eBay>Unsold summary for 60 days and for 90 days in Seller Hub.