Can anyone suggest a method to transmit/recieve at non-standard channels (to overcome high intereferce) using any linux code, or third party software?

To my knowledge, you can't use non-standard channels. You see, you will need a WiFi capable chip to manage the link and radio protocols, modulations and frequencies. Those chips come with fixed capabilities and bands set by the IEEE standardization body.

If you have high interference with WiFi, try using bang 5GHz, unlike the GHz band (which has only 11 channel, only 3 of them are non-interlapping) , the 5GHz has 36 channels to choose from.  You can use Apps on your mobile device to detect the RF conditions in your environment and select a channel.