Permission to work with Interserve Cleaners

I sent 2 emails to Interserve, requesting permission to create an artwork about their cleaners at Liverpool St station.  Both were ignored.

So this morning I rang their HR advice line (as I thought my query could be considered an Employee Relations issue).  I had a very brief phone call with a noisy call centre.  The young male HR adviser asked whether I knew anyone on the site concerned, which I do - I've spoken to the Cleaning Supervisor, who was very enthusiastic.  I was advised to liaise with the local site direct, as it was up to them.

I'm quite surprised at this, because I would have expected much more interest in compliance with company policy, and managing their public visibility/image.  However, as I used to be an ER manager, I will manage my work and myself in such a way that it won't bring them in to disrepute (quite the reverse, I hope).