Where can I sell USDT to GBP?

Good afternoon, I'm a beginner in the cryptocurrency world. I'm holding some USDT and I'm interested in converting them to GBP. Could you please guide me on where I can safely and securely make this transaction? I've heard about some exchanges but I'm not sure which one to choose. Could you recommend any reliable platforms or methods? Also, are there any fees or commissions involved? And finally, how long does the whole process usually take? Thank you so much for your help.