Singing Pig

I came across the term  "conditional exchange" and I think it was n relation to locking someone in so that they don't sell while you are doing a survey etc. However, I thought an exclusivity or lock out agreement did that.  Is a conditional exchange preferable to an exclusivity or lock out agreement? 

 It sounds like it would probably be cheaper.
 

Conditional exchange is normally used when waiting for the outcome of say a planning application so I will exchange conditional on you getting planning for 3 x 4 bed houses - if you dont achieve the planning you thought you were then the exchange can void.

regards