Parcels not protected

Around 3 weeks ago I bought a toy for my class from a seller. They didn’t send until the final day that they could which is fine as it’s now the summer holidays but when it arrived it was in a home and bargain bag for life. When I opened it the main part of the toy was bubble wrapped in a few sheets but broken - it’s a light box so you would expect it to be in a box but of course it wasn’t. The surface had gone straight through with wires exposed so obviously not safe for use. Also came with some toys to use on it, they weren’t damaged. Immediately reached out to Vinted about it being damaged and it has taken them over a week to decide whether I would be refunded or not, after me sending multiple messages this morning. I have now had the seller message requesting it back. I still have it, I just don’t feel comfortable sending it back and paying for the postage of this item without it being through a Vinted label. Weird since they insist that everything must be through Vinted but then the seller states Vinted have said for us to arrange between ourselves. Such a hassle and waste of time!