hi kadunk,
The psu is NOT isolated from the mains supply and I would recommend that you dont build it.
They are mainly used in enclosed devices where the 'user' cannot come into contact with any part of the wiring.
If you ever plugged it into an incorrectly wired mains socket, ie reveresed wired, the psu and the circuit
its powering would be at the mains potential
Buy a simple 'wall wart' , with an output voltage of say +15V, 1A and use two regulators on your board
to give +12Vdc and +5Vdc, it much safer to have the mains isolating transformer.