What exactly do you mean?  Do the two halves of the plug/socket not
come apart?  There is a plastic doohdad that you squeeze and they should
easily click apart.  Or are your connectors the bullet type?  They may
be corroded together.  WD40 them.  If you're trying to get the
individual wires out of the plug, I'm sure they weren't designed to do
that.  I'm in the dark here as I don't know exactly what connectors you
have, but the XJ40 has snap together connectors all over the place.  As
a general rule, everything is designed to come apart for replacement
etc.  No wires should ever have to be cut, or metal flanges or
whatever.  Reminds me of the Jensen Interceptor I once had.  You cannot
clean one of the spark plugs without removing the engine and
transmission!  But that's unusual; I've never come across that in any
other car, and some to think of it there's probably a special tool for
the job....