T-1 alloy steel plate would not be any more difficult to machine than stainless, and it's got far greater strength than any SS unless the SS is a heat treatable alloy and has been heat treated. Most folks get the idea common stainless alloys such as 304 are strong, but that's not the case. They're just difficult to machine. Yield strength for T-1 is 100,000 psi. minimum. The ASTM designation is A514. You should be able to use this to find a European equivalent. It's economically priced because its produced in large volumes for the manufacture of heavy construction machinery. Price should run about 1.5 times the price of mld steel. It's available in thicknesses ranging from 3/16 to several inches.