Make what you can and buy what you have to
Hi Sonar
I used to look round the local tip but it is now prohibited in my area (Cheshire).
I agree many industrial sites have waste skips but as you suggest it's best to obtain permission before removing items.
Another source is Freecycle where spare items are offered for free, but you do need to be quick as popular useful items are quickly taken.
Another source are bring and buy sales at model boat shows etc.
Live long and prosper
Dave