Yes, you retain copyright over your material. We would encourage you to share code samples with a permissive license (e.g. MIT), and any slides/material with something equivalent (such as CC BY-NC or BY-NC-ND). By agreeing to speak you grant us the rights to video you and your talk, and to use that video in promoting Bristech.
The Bristech conference offers a unique chance to hear many local tech speakers, selected both for their relevance to the modern software development landscape as well as a proven ability for insightful and engaging talks: