Complex sentence: Being the Saturday after Pentecost, the canons had arrived on the eve of the town's annual fair and all the inns and lodging houses were full with merchants, but one group of merchants kindly vacated their rooms in a newly-built lodging house.
Split into simpler sentences: Being the Saturday after Pentecost, the canons have arrived on the eve of the town's annual fair, so all the inns and lodging houses are full with merchants. However, one group of merchants kindly vacate their rooms in a newly-built lodging house.