As the queen came with a swarm, the chances are that they will swarm again
Quite possible but depends on a few things. You don't know why they were a swarm in the first place; could be that the husbandry was poor, if lost from a 'managed' hive, or it may be a trait of the strain. She is less likely to swarm a second time - my bees would generally supercede before they went again. But one can never be sure...
If your queen was marked, you may know whether she has been superceded in the autumn (many don't inspect, as much, later in the season and are often unaware that supercedure has occurred).
do I leave the queen a brood and a half or what.
Great to be thinking ahead, but impossible to make any sensible recommendations on the information supplied, so far in advance. I suggest you get a few pieces of blank paper and draw out several scenarios - single brood, brood and a half, double brood, etc. along the guide lines given above. Then, in the spring, you go with the appropriate plan - because neither you nor anybody else knows what the circumstances will actually be, come springtime.
RAB