Where can I find/buy clean animal bones?
It’s a shame you don’t live in the USA, there’s several companies that carry what you need. But shipping to the UK would be overly expensive. You can, however, contact these companies and ask them if they know of a UK or European company that you can contact. An alternative–check with local farmers about dead livestock they may have let decompose on their property–could be old sheep bones, deer bones, dog, etc. available. Insects clean off the surface, you only need to dip the bones into a bleach bath (1 part bleach, 10 parts water) in a bucket for 5 minutes to sterilize and whiten them. Hose the bones off, or rinse in the house, they’ll be ok to use then. I’ve used this technique with deer shoulder blades I’ve found in the woods and bird skulls I found at the lake front. The delicate bones need less time in the bleach water, as the bleach will do damage to very thin bones.