Problem: can't get an answer from the Performing Rights Society (PRS).

With the centenary of the War coming up next year, I'm looking into the idea of performing some of the well-known popular songs that were sung by the Forces and at home. This would most likely be a not-for-profit and/or fund-raising event at a small (probably fewer than 50 attending) venue on the Isle of Wight. While I expect some of the material will be out of copyright by now, I think quite a few pieces will not be.

My main source is a Daily Express community songbook from 1930. The publishers' names are given, but none of them seem to be contactable on-line; I dare say some of them will have been taken over by other publishers anyway. Some of the original sheet music I've seen specifically states "may be performed in public except in theatres & music halls"; I presume this still applies, if I can show the evidence. I've emailed the PRS ... and got an out-of-office reply:
... We will endeavour to reply within 3 working days, however in busy periods this is not always possible ... To enable us to deal with your query please provide your PRS for Music account number on your email.

Obviously, I haven't got an account with them! Does anyone have experience of this kind of thing? Do you know who I can get in touch with?