Dwarf Yellow Broom or Genista x spachiana.
I have a love and hate relationship with these plants. When in flower, these guys fly out the door, the bright yellow flowers sell themselves. However, if not all sold in flower, these things will sit on the shelf for months before having to be heavily pruned (hacked) then fed with a high Nitrogen fertilizer and regrown for hopeful sale months down the track. This additional work really detracts from the profit margin, especially on a small 140 mm pot.