What solvent to use to remove metal letters fixed on glass with UV Glue?

This can vary depending on the particular UV adhesive used. One of the easier to get solvents often used is acetone, available at most hardware stores.

ANS 2 The best way of doing this is to heat the letters with a hot air gun, then slide a wood chisel under and force the letters off. The remaining residue can be removed with MEK or possibly acetone.