Fitting dishwasher in existing kitchen with plinth etc?

I agree with the above. Remove the old unit, this will be screwed to the adjoining units and to the worktop above.If you have difficulty moving the plinth forward, screw in a couple of screws in the area where the dishwasher is going and pull forward (screw holes wont matter as you will be cutting this area out anyway). After cutting plinth to fit against dishwasher sides, seal the ends with paint or varnish to prevent the chipboard from absorbing moisture and swelling.