Ok so I have completed this job - almost!
Tiles went on beautifully and as hoped. The time invested in carefully grinding curved tiles (bosch multi tool) really paid off.
Errors: too much water in the grout ruined it. Redid that using a correct measuring device in the form of a 60ml bottle.
😀
Victories:
overall look of the handmade tiles, is stunning.
Grout turned out beautifully and added to my upper arm stamina - all that vigorous polishing the grout off/out.
Variations in gaps (minor) added to the overall effect.
Masking the bench AND close to the bottom of the tiles produced and excellent junction between the surfaces. And fingers (rubber gloves actually) with detergent really does work when removing excess silicon.
Remaining challenge: tried to silicon the exposed vertical edges. Then tried no more gaps ... I was not happy with either outcome.
Any ideas/suggestions greatly appreciated.
Pics will follow when taken/adjusted.