Aisha.. Its difficult to get that done.. however you can ask for a remeasurement with your presence... that way you can catch on the extra measurements.. and regarding the drawings check the tender if the unit is item.. if the unit is nos. there is nothin much you can do.. And Tiling also can be remeasured..

Regarding the delay, check if there is some paperwork from contractor's side?? Maybe some things were delayed from ur side or the consultant's side.. If not, you better check if there a clause in the agreement for delay & the penalty against that??