Vince, just as an extra bit of information you might need……….
I know how inviting some bits of lumber can be :-) Take for instance railway sleepers (I believe you gentlemen “across the pond” refer to these as railway ties). Great slabs of wood, well seasoned and preserved for the outdoors and just begging to be turned into garden benches/projects, well dont!
Take it from the guy who made some raised flower beds with them. Looked lovely until the summer came and they got hot and then they started to leach creosote and tar. You tend not to notice the penny sized wet patches when you are gardening and standing on them but guess what happens when you track creosote and tar into the house………yep, move over dog I’m bunking with you tonight :-)