Best way to replace a lawn

Hi

We've recently moved house and the garden is in a frightful state.  The lawn is full of moss, weeds and clover as well as being bumpy and uneven.

We've had a few quotes to level the area (around 10m x 20m) and lay new lawn, however, each of the contractors has a different method for removing the old lawn.

My questions is simple.  Would you;

a) Just rotavate the area as it stands;

b) Use systemic grass killer, wait until the grass is dead and then rotavate;

c) Use a lawn cutter to remove the grass, turn the turf over and use it to level the area before dumping top soil on and laying new lawn;

d) Other?

All suggestions welcome.  If all the landscapers had agreed the choice would be a lot easier, but we've had three contractors round and three different answers!