I don't know about lumber in the UK but here in the US. Most pine is ok but i don;t like or use it. "treated" lumber is treated with chemicals and pesticides that help it survive in outdoor and ground contact situations (like building a porch).I think there;s some confusion between "lumber" and wood for perches. If your looking for something to use as an upright to support your perch/playgym, then something like "closet rod" or hand rails for stairs would probably be OK because it;s something your bird won;t be prone to chewing on.Natural branches (IMO) would make much better perch of lots of reasons but you need to research what is safe in your part of the world.There are places i would avoid collecting even safe woods from, like road sides, orchards,places that herbicides and pesticides might have been applied.I don;t soak perch materials in bleach but place them in sunlight to dry and small peices can be baked in the oven. Your main concern is with things that wild birds might have left on the trees that could be transmitted to your birds.Most of these type thing survive longer in a wet environment so drying should inhibit their survival. Drying will also help to rid the sap from fresh cut branches which is the part of most trees/plants that make them toxicI wouldn't stress too much about bugs in the wood as they are mostly interested in eating the wood and not your bird (ants might be the exception). PS if you use wood products from the store make sure they aren't "finished" with anysort of paint/lacquer products.