I have a new seat belt to fit to a 57 plate octavia, when I unplug the electrical connection, will it need re setting on vag com.

Is this the plug on the female part of the buckle? If so then no, if you leave it disconnected then the light and bongs will not happen either (may be worthwhile as a taxi driver?)

If it's the pre-tensioner on the belt ratchet itself then I am not sure, remove the battery earth cable whilst fitting it and you will be fine.

The only plug that should need a reset is the yellow airbag plug, then only if the ignition is turned on whilst the plug is disconnected.

Thanks for the reply, it is the pre -tensioner, so i will disconnect the battery.