Stamp duty land tax is a personal tax which the buyer is responsible for. It is a self-assessment. Your conveyancer only acts as your agent and it is up to you to confirm what duty and reliefs you believe apply to your circumstances.
If you get it wrong the revenue can take action and investigate post completion
It is a criminal offence to defraud the revenue
This applies to both HMRC in England and the Wales Revenue Authority.
Best not to get caught out.