I will be travelling to Phoenix, USA via London with valid US Visa and onwards journey boarding pass with Indian Passport. I have 18+ hours layover in London. I want to know How likely is to get the 24 hours transit in London. Its a long time and I don't want just to waste it by staying at airport. I want to go to hotel to have some rest and then probably visit some places. I can see I come under "Transit without Visa concession" but I heard it depends on visa officer to allow to go out or deny. If they won't allow Will I get visa on arrival.

Also I tried to apply for Transit Visa. Its asking me Whether you want to go for sight seeing or not. I said Yes. Its saying me you have to apply for different visa. If I am going out of airport then its natural I will go for sightseeing? I just can't close my eyes and roam around. What other reasons would be there to go out? What do you guys suggest? What to do? I am totally confused.