Can't use bluetooth or use internal/external speakers

[Padwen]

Hi all

Suddenly my MBA has all these problems. The battery bar went red for a while a couple of days ago - I was having a problem with the charging cable at the time. It returned to black after a couple of restarts. Since then:

• Bluetooth is showing as not available
• It can't access the internal speakers
• A connected external speaker doesn't work
  
• I can't reset the p-ram. Instead of making the start-up sound, the screen just repeatedly greys. flashes quickly and then goes black again.

I've tried all the things I know - disk repair utility, hardware diagnostic, reset the SMC but none of these have worked. I'm a long way from a repair centre, so I'm hoping there are some options I haven't thought of to try and fix this myself.