If you're reading this, it's probably too late because you've been stung, BUT... just in case.
My colleague and I paid Madison Brook the full moving in fee, as we were told our offer had been accepted, however, it hadn't. The deal fell through, and we spend month after month trying to reclaim the money (several thousand pounds). In the end, we had to chase MB through the courts, and only after a successful claim against them and the thread of enforcement did we get our money back.
I ended up keeping a spreadsheet of all communication attempts to them, by the end of it there was over 70 phone calls, 25 emails, several letters... an absolutely despicable company, I'm shocked they're still allowed to trade.
Full disclosure: this all happened last year.
What agent could do to change your mind?
Returned the money promptly once it was realised that the deal had fallen apart. No undue "internal complaints procedure" - 21 days. They're a tiny company for crying out loud. Return calls. Respond to emails.