I got some lengths of 1" quadrant from my local plastics merchant siliconed the gap wiat for it to set then siliconed the quadrant on top, left it watertight and look professional as well, took some time to create a tight mitre in the corner but was well worth the effort.
http://www.wickes.co.uk/PVCu-Quadrant/invt/162617?source=123_4
Billy Nomates
January 2010