How long Survey to Completion

Hi - the people buying our house have used a Broker and a legal panel and have got a mortgage with the Abbey, the survey was paid for over three weeks ago and they have only just booked with us to come and do it on Tuesday - apparently this is the way Abbey do things, everything else in order then the survey ?? Our buyer is as frustrated as we are at how long this has taken but is under the impression that we could still aim for completion by the end of May - Is this feasable?? Our Solicitor was against being optimistic last week this was before the survey was booked so surely May completion is out of the question now?? We have obviously not booked removals or anything as we had no firm date and it would be too short notice to do it now. There has been no date set by any of the Solicitors so should we assume our buyer is just wishful thinking - Any insight would be appreciated thanks