Hi John,
Is it this one ? (By a different Andy)
https://britastro.org/2017/guide-to-processing-spectra-using-the-bass-software
It is linked from the Spectroscopy resources page of the equipment and Techniques section here
https://britastro.org/section_information_/equipment-and-techniques-section-overview/spectroscopy
which used to be given in a sticky post at the head of this section of the forum but seems to have become unstuck !
Cheers
Robin