Thanks all for the helpful info.
I went completely sideways on this one. I have a Marantz pm4200 which i really liked but it used to cut out regularly on me. It has been shelved in the attic for the last number of years ready for recycling. I started reading up about this about a week ago and it turns out speakers outside its recommended impedance can easliy trigger the cut out circuit. I was using JPW ML510 that were 6 ohms. The manual says use speakers between 8-16 ohms. I instead bought a set of Cambridege Audio sx-50, 8 ohm bookshelf speakers. So far so good.
For anyone interested Chrisr1718 may have a great deal on an amp if needed, I didn't require one after all.