if buyer requests for annoyingly impossible tasks from you, then i can understand your sentence right there.

but buyer now is only requesting that you send the parcel to him, and it's not really a big deal/will take hours of your time innit? and it's bloody reasonable as well that you post it to him instead of him going to your place. why so much trouble? plus, i believe that's what your 'friend' was supposed to do - post him the panel.

ps you talk about how busy you are and everything (therefore delaying posting and everything). i believe, no matter how busy you are, you HAVE TO give some time for after-sales service etc. if you're too busy even for that, then i think you should not be doing business here. who wants a seller who delays sending things all the time because he's simply too busy???