After much eye-popping template trawling (which proved to be a complete waste of time as it was somewhere else

), I have found out why the WYSIWYG editor wasn't working, interested? then read on
Go to you
all style options for the hardwired style in your AdminCP.
ctrl+f and search for
Text Editor Control Styles
for the bottom 4 that say
(WYSIWYG only)
They will all say this:
border: 1px solid #434B55
Delete the first bit leaving just the colour in each box
#434B55
Works a treat for me, hope it works for the rest of you with the same problem.