Ok so i took the plunge and tried out this out so it can finally actually be answered for any others!
So I was sent an offer on an item I wanted, was £16.95 but £15.95 offered. I noticed on the regular item page the current 10% eBay code did show I can use it for this purchase. I accepted the £15.95 offer and on the payment page I was then able to enter the 10% code in the voucher box, I did get this to work. I got the item at £14.35 paid in total. *Test* ✅
Hope this might help someone else wondering about using a current voucher code still, after accepting an offer sent from buyer. The one thing I’ll say is to make sure the code is useable for that seller and that item, before then accepting the offer and entering the code at the payment stage to further reduce amount paid 👍
Happy eBaying and saving pounds where possible! 😊