Thanks for the info. This turned into a bit of a saga with Dell. I already had a spare Xeon processor which I intended to use. Unfortunately the power connector on Intel branded heatsink fan, was of a totally different design to that accepted by the motherboard. I tried to order another fan from Dell but was told not possible - despite the fact I had the appropriate part no's.
I eventually asked Dell if I could order the entire heatsink assembly. They said yes no problem but they had none in stock and couldn't tell me when they might do.
The only option left was the order the complete additional processor kit from Dell. This includes the processor, heat sink assembly and clips - and costs £350! Expensive when you can pick up a Xeon for around £140.
Pauly