Iomega External HDD Safety

I recently bought an external 320GB HDD, the power switch for which is at
the back. A few times, when reaching around the back, the back of my hand
touched another device and I received a slight electric shock. On
investigating I found that there was about 80V AC to earth on the edge of
the metal case. The HDD is connected to a Linksys NSLU2 NSA. When this is
switched off, the voltage on the HDD drops to about 40V AC.

I found that both PSUs had this voltage on the outer connector of their
power lead. Neither psu has a ground connection. A replacement psu from
Iomega has the same feature.

As the HDD has no earth, but does have a metal case, what are the safety
requirements, if any, in the UK?

Thanks

Allan