Ilford 500H vs. 500 HUL Enlarger Head

Does anyone know the difference between the Ilford Multigrade 500H enlarger head and the 500HUL version? One of the latter has shown up on eBay and it might be suitable for me, although it lacks the power supply and control unit.

Are you sure it's the 500HUL or are is it the Ilford 500HLZ. Ilford made the 500HLZ for the Leitz IC enalarger. The head is smaller than 500H and it came with a light mixing box only for 35mm negs. Also this head does not have a cooling fan for the bulbs and the bulb wattage for the head was two 80 watt bulbs instead of two 300 watt bulbs that the 500H uses.