At what point does it become theft? When he sells it to pay for his "fees" ?

I spoke with C.A.B and they've told me to write a letter to the courier to cancel the contract under: Consumer Protection (Amendment) Regulations 2014 Due to his misleading and aggressive practises. The courier text me today and told me he will not allow me to take back my sideboard or use another courier to collect the sideboard from him, not until I pay the full quoted fee from shiply, plus any charges he adds on (£3 a day cr*p). He also said he was selling my sideboard to cover the fees if I don't pay him! Cheeky s*d!

I bought something online then used Shiply (for the first time) last week, all went well until the courier who agreed to pick up on a certain day then went on to pick up on a completely different day, to the sellers annoyance, then when they picked up on the wrong day the driver text me and demanded payment by bank transfer! I only used them because on their Shiply account it clearly says Paypal as one of the accepted payment options! The courier text me (they will not answer calls or any emails!!!) and said that they do not use Paypal and they would be charging ME £3 a day to hold my item, until I paid, by the most unsafe way ever... bank transfer! I contacted Shiply who said i'd have to sort it with the courier myself, what the hell? Shiply took a deposit from me and then wash their hands of it. How can that be legal? Surely if the deposit was sent to them then they are just as culpable as the courier