Routing Problem?

Hi,
I do hope this is the correct thread to post this in, apologies if not.
It might also be specifically an OpenELEC problem, but I thought I’d try here first.

Our setup:
Raspberry Pi 2 running OpenELEC / Kodi, with a USB HDD connected, our CDs and DVDs ripped to the HDD. RPi is wired to my (Virgin Media) router, and connected via CEC/HDMI to our Sony Bravia TV. The TV is also wired to the router.

PCs around our home use a local installation of Kodi to access the media centre and it’s hard drive, hence able to access music and movies.
Smartphones and tablets use Bubble UPnP to access our media centre.

Where we can use the media centre:
On our TV, and on the PCs that are wired to the router.
Also on tablets and phones anywhere in our home via Bubble UPnP.

Where we can’t use the media centre:
On any PC that is wireless connected to our LAN. It seems as though our media centre sees this as a separate network and won’t talk to it (?)

Any clues?

Thanks in advance.