Complex sentence: The late Dave G. Halliday was the singer/guitarist from the band Hell, the Derbyshire band who in the mid 1980s were a big influence upon and inspiration for Sabbat.
Split into simpler sentences: The late Dave G. Halliday was the singer/guitarist from the band Hell. The Derbyshire band who in the mid 1980s were a big influence upon and inspiration for Sabbat.