Similar incident here!!!
I sold my XS for £700 couple of years ago. Met at the station where I knew there would be CCTV.
Buyer gave me £700 cash, all in £20 notes.
Went to the bank the next day and the deposit machine wouldn't take the notes - I was then told they were all fake notes - the bank were surprised at how good they were!
Contacted the police etc who told me to contact BTP as the deal had been done at the station. Contacte dthem and they didnt get back to me for 3 weeks even after I chased multiple times. In the end it was too late - they had overwritten the footage!
I complained. Because of this they assigned someone to the case.
After tracing the IMEI to a sim that was now in the handset, it turns out the handset was sold on Amazon to someone. Police traced the person, who said they had sent it back to the seller just a few days before - had receipts etc, everything checked out - so just missed it!!
Amazon would not disclose any information on the seller to the police.
To cut a long story short - it took a WHOLE YEAR or waiting and chasing, and tracing the IMEI etc. In the end they found the Amazon seller and had enough evidence to issue a conditional discharge.
Finally got my £700 from him via the courts!!!
I don't want that stress again!