The risks of contracting HCV through tattooing are mainly associated with re-used and unsterilized needles, although the virus has also been found in tattooing ink.
The hygiene standards of tattoo parlours in the UK can also differ. This is because their regulation is carried out differently depending upon where in the country the parlour is located. Like piercing salons, this tends to done by either local authorities, in some cases (most of London) licensing and in other areas by byelaws.
The Department of Health have produced a model set of byelaws (click here) that set out the standards that you ought to expect from a tattooing parlour. You are unlikely to find these standards in developing countries. Tattooing with re-used equipment in high risk countries is a significant risk, as is tattooing in prison in the UK