You can decide your other HA independently for sure.

Sieghard can see there are a couple of small, shuttered windows on the ground floor. For him to get through either of them would be a squeeze even without his armour on. With his arms and armour, and with the Tileans behind him and able to grab his legs, it seems next to impossible.

He can see that the mill's mechanism is inactive. He can't see any kind of lock or switch on this floor.

He can see that the stashed stores don't look like they have been kept sealed - there are open boxes and half-empty sacks. There are a couple of handcarts that have been used to move them, still laden with sacks, that could be used for a makeshift barricade (though it probably wouldn't slow the Iron Company for much longer than it would take Sieghard to set it up).

He can see that there's more light coming down the ladder from upstairs than there is coming in from the ground floor windows. The floors are quite high-set though - any jump from an upper storey would be a risky one.