How do I sell my BNB for GBP?

Could you please elaborate on the process of converting my BNB tokens into British pounds (GBP)? I'm a bit unfamiliar with the cryptocurrency exchange process and would appreciate a step-by-step guide. Firstly, which platforms or exchanges support this kind of transaction? Secondly, what are the fees associated with converting BNB to GBP? And lastly, how long does the entire process typically take? I'm looking for a secure and efficient way to cash out my crypto holdings, so your advice would be greatly appreciated.