Between 15 and 20 years ago I went to Leeds, Birmingham and London South Bank. All were lovely and there was a lot of variety between the stalls.
The last 5 years or so they have been absolutely rubbish.
Lot of nice smaller ones put on all over the place, though - an Etsy-organised one for makers within 40 miles, a couple at stately homes or in pretty villages like Ruthin or Saltaire where it’s mostly independent makers selling their produce. I love a chance to buy something a bit out of the ordinary.