Thanks all for  your input.

I will be travelling with 3 year old, so i am really hoping to be able to get a room, as i can see heathrow airport site clearly says there is no place to sleep anywhere inside airport. Before booking my ticket to Nepal, I knew Yotel rooms were in terminal 4,and i will be landing in T3 but what i didn't know  switching terminal  would be big deal.

I  have 3 weeks left, before i leave for Nepal. Is less than three weeks sufficient for me to  apply and get get UK visa? I  will apply for something like 24 hrs visa, has anyone done that? can i get the visa at airport itself?