IIRC, which is far from guaranteed these days, I fitted some 'stats similar to these a few years back. In spite of having terminals for an external thermistor, they were actually fitted with internal sensors. The terminals were fitted for a different version of the 'stat which did need an external probe.
As for connections, connect N, L and L1 on the 'stats to the corresponding terminals in the control box. I expect the N1 terminals on the 'stats are internally connected to the N terminals (check with an ohmmeter) are will be unused.