In message .com,
mjbarnard writes
Installing kitchen cabinets into utility room. Using a 1000mm corner
unit. There is a base unit corner post to offset it from the connecting
units along the adjoining wall.

Looking at the corner post, the sensible sequence to line everything up
seems to be - fit doors to both units , then line up corner post
between the two doors and fix to base unit.

Is this right?
More or less. Usually there's some dimension info in the assembly
instructions or there are pre-drilled dowel/screw holes to fit the
corner post.

And if so - is it then possible to join the two cabinets together?
Units in a run are obviously easy - but in the corner (due to the
corner post) obviously there is a 3cm gap between them. As this is a
very small room with only a few units, would prefer to join them
together if possible (for stability).

Yeah, that 3cm gap is where all the contents pushed into the dim and
distant recesses of the "corner" cupboard disappear! I normally close
off the "hidden" open face (IYSWIM) with a sheet of MFC - generally
you've got a few carcass end panels spare from where "decor" ends have
been fitted. Add a bit of packing up to the depth of the corner post and
you've then got something rigid to screw / bolt through to the adjoining
cupboard.
YMMV.

--
steve