What you have to do is register a company offshore and in the UK. The offshore company purchases all the stock at say £10 a unit. The offshore company then sells it to the UK company for £19 a unit and the UK company finally sells it to the end user for £20. £9 off your profit stays offshore.
However you pay tax on the money when you being it back in to the uk.
So one option is to have an offshore credit card and use that in the UK but only on disposable items hence they are not traceable or tangible.
Finally it is not recommended as tax evasion is a criminal offence and you will end up with big billy hanging out the back of you in the showers.