@bythewell - The problem for me with this kind of stained glass art is that, while beautiful, if it is put into steps the sun can never shine through and show the true beauty of the glass. I particularly like sea glass mixed with normal glass, because of the different contrasts of those textures, but that's more difficult to see if there is no light involved.
If I was going to try and make something from local sea glass it would be with the soldering method, so that it could be hung up in the light. It would probably be more lumpy than the average stained glass mosaic, but I think that could make it more interesting as well.
And you would be able to create a meaningful piece with much less glass than you'd need to cover an entire set of steps.