This is part of the London to Belize and Guatemala trip December 2019. http://dickandsuegotravelling.com/2019/12/detroit-usa-to-belize-2019.html
Pre-flight Ibis Hotel Bath Road Heathrow Airport LHR to Chicago MDW.
The first night finds us staying at the Ibis Hotel, Bath Road, just outside of Heathrow airport (LHR). The rationale being that we may struggle to get to the airport early on Christmas day. The London underground does not run on Christmas Day.
When travelling to the Ibis Hotel, Heathrow or any of the hotels along Bath Road, if you go to Heathrow Airport and get the shuttle bus it will cost £5 each way per person. Check the TFL Transport for London (TFL) Website and get a normal bus to Bath Road. This can be picked up from the the central bus station between terminals 2 ND 3. There are about 4 buses that go to Bath Road, and take only a few minutes. The fare is £1.50 each. A lot cheaper.

You need to factor in the cost of the hotel and food to decide if this is a cheaper option or get a taxi on Christmas day. The hotel was £49.
Flight to Chicago
Xmas morning and we decide to take the shuttle to the airport at 5.40am. The shuttle only runs once an hour on Xmas morning and will be the enhanced Xmas rate of £6 each or a taxi for £15. We settle for the taxi.
We flew economy on Delta Airlines, DL17 to Detroit. Although Xmas morning, there were no signs of Xmas on-board. I had a tasteless Cheese omelette for my breakfast, we left at 9.30 washed down by several glasses of free red wine. I had read that we are given a pre-flight drink of Prosecco mix, a form of Bellini drink. This was not pre-flight, but very nice anyway. The alcohol was free flowing and free. Snacks are available through out and the films.etc on the IFE were of a good quality. One film, ANNA, was listed as lasting 1 hour and 60 minutes!

An ok flight in economy.

Flight transfer, Detroit Airport, DL17.
Only 1 complaint was that we were transferring at Detroit onto an internal flight, but nobody told us how the procedure works. Obviously we need to go through passport and customs. But is there a separate queue? It seems half the flight had the same question. The procedure was quick and easy once someone had explained it to us, and individually to the other 200 passengers.
A quick Delta airlines transfer flight to Chicago on Flight Delta 3514 to Chicago Midway Airport.

Chicago Midway airport to Downtown is via the orange line on CTA transport. Cost was $3 each, and took about 30 minutes.