I never buy my postage on Ebay, but I imagine the information you're looking for is in the Seller Centre (link at foot of any page), along with everything else you need to know about selling here.
I do however know that Hermes, who Packlink use, have a maximum parcel length of 1.20 metres. If I were you, I'd buy the postage at the Post Office, as Parcel Force's max length is 3 metres, I believe. You can also buy PF postage online, and arrange for them to collect from your home if you prefer.
Other carriers also offer this service. Just do a web search to find one which suits your needs and your budget.
@theenglishgentlemen
