Transit Visa at London Heathrow Airport- change of terminal

[lawques]

Hi , I am on F1 visa and going to India for the vacation. I have a flight with a stop over for about 2-3 hours at Heathrow Airport,but I will be arriving at London from different airline and then I have to change the terminal and depart from another airline. I thought since I am not leaving the aiport any time I do not need a transit visa but many people told me that since I have to change the terminal I need to get a transit visa. I am confused what is right and wrong. I also called UK embassy and they gave me a site but that did not gave me a clear answer. So please reply to my question asap, your help is appreciated.
Thank you-

 

[nkm-oct23]

If you have a valid US visa in your passport, you don't need a transit visa. Make sure that the visa stamped in your passport has not expired or will not expire when you pass thru London.
Please see http://www.ukvisas.gov.uk/en/howtoapply/infs/inf20transit#23021415 for an official statement on transit visas.
See under section called "Am I exempt from the DATV requirement?"

 

[lawques]

Thank you Very much for your reply..