Examples of lines studied in the present paper. The reference spectrum is indicated with a solid orange line. Absorptions from the ISM, from the three LVCs, and from the circumstellar disc are shown with dotted, dashed, and solid grey lines, respectively. The full model, convolved with the instrumental LSF, is shown with a solid black line. The observed spectrum is shown in blue; error bars only reflect the tabulated uncertainties and do not include the systematic uncertainties of our model (Sect. 4.8). For each line, the corresponding species and lower level energy are indicated in red. Note that the Fe II line profile at 2494 Å results from a doublet of two lines separated by about 0.1 Å.