U.K. and Ireland - Spending a night at T3 - LHR

I am scheduled to arrive at LHR at 1755 from DEL and Depart the following day to LAX. The carrier is VS. VS301/VS7 connection has a 18 hour layover. I am an Indian national and hold a valid US Visa. Though I am prepared to spend the night at the airport (T3 Airside), can someone let me know if I will be asked to leave the airport

I am scheduled to arrive at LHR at 1755 from DEL and Depart the following day to LAX. The carrier is VS. VS301/VS7 connection has a 18 hour layover. I am an Indian national and hold a valid US Visa. Though I am prepared to spend the night at the airport (T3 Airside), can someone let me know if I will be asked to leave the airport

Welcome to FT!
You can't sleep airside at T3.
Take a look here http://www.sleepinginairports.net/europe/londonheathrow.htm
Suggest you find a hotel. Yotel is likely cheapest.

Welcome to FT!

As UAPremExecflyer says, it's not possible to remain airside at LHR overnight. Yotel might not be the cheapest if you want it fully overnight, but there are definitely several hotels in the area you could stay in.

Do check that you meet the criteria for transit without visa in the UK. Delta provides free access to the TIMATIC database containing this information here (https://www.delta.com/planning_reservations/plan_flight/international_travel_information/visa_passport_information/index.jsp). It seems that Indian nationals doing TWOV in the UK tend to be subjected to heavy scrutiny, so I would carry documentation of what you plan to do in the US (if you'll be studying or working, documentation to that effect) so that the UKBA agents don't suspect that you're trying to use TWOV as a way into the UK long term.

I think the worst-case scenario is that you are not given leave to enter and get put in the immigration holding area all night and sent on your way the next day.

But UK Border Agency can be very odd.

I think the worst-case scenario is that you are not given leave to enter and get put in the immigration holding area all night and sent on your way the next day.

But UK Border Agency can be very odd.

Does anyone know of any stats out there regarding how often that happens, and to whom?

Can u please tell us what happened to you ? did they let you sleep in the airport or you went out ?