Visa for Tibet for British citizen currently living in Dhaka

You can first obtain a China tourist visa to enter Mainland China (at present, you can't enter Tibet, you can enter Beijing, Shanghai, Xian or other cities), please don't declare that you will visit Tibet on the visa application form, then contact a travel agency in China to obtain a Tibet Entry Permit for you, at last take your passport, China visa and the Tibet Entry Permit to visit Tibet.