The BBC is involved in the RES (Research and Education Space) project. It is an initiative to improve access to archives for educational purposes. The BBC has just put 16,000 sound effects from its sound library online, directly accessible to the public!
The files are available in WAV format and can be downloaded and used under the terms of the RemArc license. In practice, they can be used free of charge for personal, educational or research purposes, as indicated in the license.
For commercial usage, you can purchase a license from our Pro Sound Effects colleagues.