The band were members of Pluck & Squeeze from Cardiff.

Lorna & Pete Davies on accordian & guitar (he built it himself - a Selmer copy),
Heulwen (sorry, don't know here surname) on fiddle,
and Phil Thomas on bass.

Dr Who eh?

You can see the building where I work on the Bay shots in Torchwood though.

Jamie & Grainne Smith from the band Mabon used to be occasional extras on Dr Who.