have you tried adjusting the pedal height ?
Tell us more re this mate 
OK. I've put this in the plainest way I can, but have still probably tripped over my words.....
On Omega B, there's an ability to set the brake pedal height, which of course also takes slack out iof the brake pedal.
what you're achieving :-
I use this feature to set the pedal height exactly to my taste, but more importantly to remove slack from the system - the annoying first inch or so of travel that does nothing.
how to do this :-
first, remove the brake lamp switch. I'm sure there's a "how to" on this, but it involves releasing the setting clamp (red plastic) and releasing the switch from its bracket. we'll come back to this later.
next, on to the pedal itself. While you're down the footwell, press the pedal a few times by hand to exhaust the vacuum reservoir in the servo and then notice the amount of slack that you have before the pedal goes hard, this is usually at least an inch, or maybe more. The actuation rod from the pedal that disappears through the bulkhead into the servo has an adjustment point - actually, the end is threaded where it goes into the brake pedal clevis, with a locking nut fitted ( 14, 15 or 16mm A/F ). It is this adjustment that you can use to remove the slack. slacken the locknut and extend the length of the operating rod by screwing it into the bulkhead, self-tightening pliers are the tool of choice. Keep lengthening until you're happy that you've removed all of the slack. Be warned, however, that you must stop before you run out of clevis to hold the end of the thread.
third, re-fit the brake lamp switch. This is a two-stage proccess involving the fitting of the actual switch and then setting it's height. On Omega B, the pedal end-stop is controlled by this switch. You have two choices here, either adjust the switch to match your new pedal position or lower the pedal position a bit and adjust the switch to match...... usually, having taken out all of the slack usually results in a pedal position which is too high to be of comfort to most, so de-adjusting the actuation rod will lower the pedal again, but you must then set the brake lamp switch to prevent any new slack appearing at the top of the pedal.
setting the switch involves adjusting it's position and clipping in the red plastic locking piece again.
in any event, remember that you're adjusting the brakes - you MUST ensure that:-
the operating rod remains fully engaged with the brake pedal clevis
the locknut is fully tightened on completion.
you will be surprised just how much play you have just removed.