If you are coming to the UK ? You used to be able to go personally to the Passport office in Petty France which is in London . Please check about ; Having to book /Location . Cost . You will be aware that the Civil service have been striking recently -Which has caused backlog.
I beg to differ - I take about 100 pounds Sterling converted to Bahts in the UK . The rates in Thailand are far better than the UK .Simple way to save money .