Paris is where you find the British Embassy (Résidence de l’ambassadeur de Grande Bretagne) in France. The Embassy is located very near to Ferragamo France. The embassy can assist you with consulate services such asor . You may also apply for a British visa if you are not from the EU to visit the UK.
British Embassy in Paris, France
Ambassade de Grande-Bretagne
Note that the time taken to issue a British visa will depend on which country you are from. some may take a week while others may take 2-3 days once you send in your passport. Check with the embassy for their processing times with regards to a British visa for your country. As with other British embassies you may want to email them first rather than to call them. Note that the embassy is close to the Canadian Embassy in France and also the Thai Embassy in Paris.