Indentation within block

Hello Alan,

I am sure it is my fault for not reading some relevant part of documentation, but I have tried while at work.

I use:
(setq c-default-style "linux"
      c-basic-offset 4
      indent-tabs-mode nil)

Everything works as expected until:

===
If(x)
{[]
===
Two cases:
1. At the marker [] if I press return a new line is inserted and always with a tab character.
2. If instead at the marker [] I press the "down arrow" and press C-o and then press the tab character there is a tab character inserted.

What am I doing wrong. It seems to only be a problem in the block. I know that linux mode uses tabs (I think) - what do I need to set to eradicate tabs.

Regards,