Namaskar,

I hold a US green card and Nepalese passport . I am travelling through Heathrow airport. I have 10 hrs layover. My flight lands in terminal 3 and i am planning to use Yotel rooms in terminal 4, and then again take a connecting flight from terminal 3, which looks like i need to take a bus to get to terminal 4 from terminal 3, do i need a UK visa for this(i mean to get back inside terminal 3 to take aflight)? any info on this will help.
Thanks
forsajha