Pre-contract lock-out clauses - can they work?

Any thoughts from solicitors on this?

LOCK-OUT AGREEMENTS
I've been having a private message discussion on our Facebook page from a buyer talking about trying to secure a property from when an offer has been accepted, subject to contract. 

Back in the '90s, we used lock-out agreements at Bonett's and, every time, it worked and the deal went through with that buyer in the mutually agreed timescale.

It didn't gain widespread traction unfortunately. We've just posted about it on our FaceBook page, Trust Me I'm A Brighton Estate Agent

Are there any solicitors reading this who could think of a way to use such a model of pre-contract contract? The purpose is clearly to give sellers and buyers security from the start.

Please respond.

Thanks,

Paul Bonett F.N.A.E.A.  M.A.R.L.A.

paulbonett@bonetts.co.uk