Luke Evans voice is lovely on The Pembrokeshire Murders - I think it’s his natural accent. I can’t say I’ve ever found the welsh accent ‘sexy’ before but he carries it well.
I like Scottish accents on women. The two that immediately come to mind are Karine Polwart and Amy MacDonald.
I also disagree with the very first post in this thread, and I actually quite like Alice Roberts' voice.
With men the accents I like are a bit stranger. Not 100% sure about his speaking voice, but I love Brian Molko's singing voice. US Senator Rand Paul also has a nice voice, but he's a complete nut, so that's the only thing he's got going for him.
Very strong Liverpool accents are annoying (eg Wayne Rooney, Stephen Gerrard). David Beckham's accent annoys me as well.