Posting PF48. Persistence and politeness pays off.
Went to my local post office today to post the MFR I've just sold. Told the posty it had to go PF48 and he asked me what was in the package. "An air rifle" says I. "You can't post those" he says, after perusing his laminated restricted items sheet. After a couple of minutes trying to persuade him otherwise I went home, dug up the 'restricted items' page of the Parcel force website, and armed with my iPad, I returned to the post office and showed it to him. Good as gold, he asked if he could take a screen shot of my iPad on his phone, exclaiming that he had never been aware of this before. I offered to take the parcel elsewhere if he wasn't happy, he would have none of it and duly accepted the parcel.
The moral is, be polite, arm yourself with a copy of the facts and educate your local posty.
Whether you think you can or think you can't, you're probably right.