I was looking Lee but 30-40 days shipping time is just a little too long but would cost me ~£10 now for 100 M4 45 series T nuts KJN will cost ~£30 but I can pick up today (KJN is 4 miles from my work). I need to go KJN anyway to cut some more extrusion for the bed and they are going to drill/counterbore the extrusion I'm making the frame from. So I can bolt it together rather than use corners which is cheaper and stronger.