If all else fails, I take one tiny Entrolax (Bisocodyl 5mg) at night as prescribed.
If you take 1 they work very gently so you don't get the trots or anything embarrassing, you'll just find you might need the loo two or three times the day after taking it, but not as a matter of urgency and no need for embarrassment.
Don't be tempted to take 2 unless taking 1 hasn't worked for you, because I did that one night and woke up at 5am with griping pains and was trotting back and forth for an hour or so.
They're very cheap, only a few coppers in ASDA or Morrisons etc.
