With many of theses products being available in the US for reportedly something between $5 to $10 but in the UK something in the region of $30, then it is not just gov taxes that account for the 200% increase. Sadly it is profiteering by the manufactures/sellers.
Take a 32Gb iPad Air. US $499 UK $785 (Â£480). Yes there is 20% VAT in the UK and local taxes in the US to be added where applicable but that still does not make up the difference.
The cost of doing business is higher at every point in the UK, not just taxes. You tend to pay more for rents and gas, for instance, which lead to greater costs, and so on. The UK also has restrictive practices on imports and labor, which leads to more overhead.
If it's just a matter of manufacturers price gouging, then the solution is simple: All an entrepreneur has to do is gray market products from cheaper places like the US.