I believe that the average British toilet bowl runs between 30 and 55bs (well it is a US piece of work). Given the density difference between gold and porcelain, if it was a solid gold bowl, then it must have weighed one heck of a lot more if it maintained the form. It must have been tricky to get in place but getting such a heavy object back out through the window (as reported) would have required heavy lifting gear shurely?
But I laughed at the 'heist' anyway. The naff being taken from the stupid (the Churchill family).