I've heard Labour spokespeople say that if the outcome of the negotiations is a 'bad deal' then they would seek an extension to the article 50 two year negotiation period and repeat the negotiations until such time they got a 'good deal'.
Of course, the only problem with that strategy is that all 27 other EU members need to agree to said extension(s).
What Labour haven't articulated (to my knowledge) is what they would do if the EU 27 refused an extension.which brings us back around to what you're saying, i.e. what would Labour do if there was only a 'bad deal' on the table and the EU 27 don't grant an extension to negotiations? My guess would be: call for another referendum