If you plan on having turf laid then you will need to remove the roots of the pernicious weeds such as buttercup, bind weed, nettles, dandelion and docks. You will also need to remove the rubbish and rubble the builders left. You can rotivate after that but remember all you are doing is turning the weeds in, not removing them. Hence the need to remove the big thugs of weeds first.

Getting rid of weed roots is a first priority. If you rotavate then all you will do is chop up the roots and make lots more weeds. Also if the soil is full of rocks/stones then you may well damage the machine. In any case if you want a decent lawn you will need to remove any stones bigger than say an inch from the area where you want grass.

Snapperama!

Thanks guys v helpful and sounds like hard work! There isnt a great deal of "builders rubble" just stones but many are more than inch so they need clearing as part of the back breaking work! If not rotavate is there a "smaller" surface machine that will just turn the ground to help? thanks again, your comments are appreciated.

Yes the smaller machine is called a garden fork and you dig out all the roots etc. with it... If you are asking is there an easy mechanical solution then 'no' there isn't! The effort you put in now prior to laying the turf will be repaid tenfold! Cheat on the basics now and you will always have a crap lawn (sorry!)

Utterly true. A little hard work now will mean a lot less later on (and save money in the long run).