You do not need to make an appointment in advance. Normally you will get your visa in about one and half hour. You can download the form in the website or you can fill it in the British Consulate there. Do take all the necessary documents with you.( I went there twice for this sake). Airticket...www.easyjet.com. You can book online with your visa card. If you fly to Berminghan, KLM maybe even cheaper.But make sure where are you going ...there are more then 3 airport in London....