I have the RNS 315 fitted with factory BT, if I was to get a 510 I know it would go straight in , but would the BT work without having to code it in with VDS 

Edited 7 February, 20179 yr by skippy41

It depends... you may have BT built into RNS315 or standalone - if standalone then it can be reused otherwise you may consider replacing RNS315 with Amundsen form new Yeti as it has BT built in as well and is much more modern unit than RNS510.

I have the OME BT under my seat, just wondered if i change , would need coded

You should have the new headunit coded anyway as it probably won't be correctly coded for your car