Tried to put canbus bulbs in my reg plate holder, didnt work, put the old ones back in, also wont work, done some research thers a fault code that needs to be cleared, can i just disconnect the battery? and will i have many side effects to this? eg (one touch windows, radio code etc)

 

I don't know for sure. Past experience indicates that will not clear any codes. They are meant to stay there for troubleshooting and history until cleared by a command.
I got my code reader from a local big box auto parts store for less then $40 and it has been well worth it. Of course around here Pepboys & Autozone will read & clear codes for free hoping you will need to buy a part from them. Good luck with it.