Two may be company, but can one be a crowd?

The 1709 Blog has received a question from a reader on the sensitive issue of what constitutes a public performance of a work. It deserves a response not only because it concerns a legal issue, one much beloved by those of us who set law examinations, involving the concept of public performance, but also because it raises questions concerning the sort of decisions that collecting societies have to make when formulating and executing their enforcement policies:

"A friend of mine runs a small jewellery shop with a workroom at the back; in the workroom he has a radio, which he listens to while he makes his jewellery. He is a sole trader.  No member of the public has any access to his workroom -- which is closed off to any public access (including from the shop itself) -- and the music cannot be heard in any public area. 

My friend is currently receiving threatening letters from PPL, demanding payment for performance of a work in public. 

Do any of you, or any of your readers, have a definitive definition of what "in public" means, for the purposes of s16(1)(c) of the Copyright, Designs and Patents Act 1988? 

PPL have their own take on it, but I can't find any legal authority to back it up:

WHAT IS A PUBLIC PERFORMANCE?
A public performance occurs whenever music recordings are played outside the domestic or family circle. Whenever a music recording is played in a commercial environment, even if only one person can hear it, it becomes a public performance and a fee is payable to PPL.

PRS seem a little more sensible:

‘In public’ means, broadly speaking, to an audience outside of his/her domestic or home circle. If the person does not obtain the required licence they may risk infringing copyright.

So PRS seems to imply that there has to be a broadcast by a person "to an audience" which makes sense - that to me is a public broadcast". If PPL are correct, on the same logic if my friend listens to music while he drives to see a customer in his car, alone, he would need a licence for that".

It will be good to know what readers think -- not just those from the United Kingdom but those from other countries in which similar fact situations may already have been judicially tried and tested or policy issues resolved.