Thanks Nick, that explains the SS function a lot better, I wont worry about changing pin 10 now.
I am feeding a row of shift registers to run a display,and the latching is done externally from the micro, so I just bang all the pixel pattern bits ( at the right time ) without using the SS function at all .
SPI.transfer(h);
SPI.transfer(hx); and so on.
I suppose I could make my 2 bytes into a sixteen bit word , but it works fine like this, and makes the lookup table smaller.
I have just noticed that I don't even take the SS low at the beginning and it works fine ..... ( a little knowledge is a dangerous thing 
I am a newbie )
On another project I take SS low and then send 50 bytes before bringing it high again to latch the registers.