Does Heathrow have lockers?

The British term is "left luggage." Try googling "left luggage heathrow." When I tried that a minute ago, several options came up on the screen. Apparently there is a facility in each terminal.

Please note that the left luggage facilities are not open 24 hours per day, so be sure they are open when you need to retrieve them. Hours vary by terminal. (Won't be an issue for you since you are leaving during regular business hours). I have never used them, but my recollection is that they are areas that are staffed by employees. They are not lockers. http://www.cheap-parking.net/heathrow/left-luggage.html

Actually, here's a better website: http://www.left-baggage.co.uk/heathrow_baggage_storage.php

Your long layover may be a bit less than you hope. Arrive 10:00 - if on time 60-90 minutes for disembarking, walking, immigration, customs - 11:30 15 to get to Tube station, ticket, wait for Tube - (I haven't booked you any time to find the Left Luggage and get the luggage through their scanners)
51 minutes according to TfL - Piccadilly to Boston Manor Station, take bus E8 to Brentford Rail station, wait for train, take Southwest Trains service to Chiswick Station now its 12:36 find ground transport to your lunch spot, and get in, just at the peak of the lunch hour. If it takes you a round hour to get back to the airport and you need to check in 3 hours ahead (do you?) you will need to finish lunch around 1 o'clock. Sorry. (might be quicker - ok it would be - if you grabbed a taxi, and booked one to take you back.

Hmmmm, Nigel, perhaps going outside the airport will just create more stress than it's worth. I really just want to have nice british meal, and feel like I have been to the UK. Any suggestions where we could go in Heathrow for some good fish and chips? Thanks, Cynthia

Yes, you have an awkward time slot. Too long to hang around the airport and too short to see much of London. You probably don't need to be back at the airport until about an hour and a half before flight time - to collect your things from the left luggage and go through passport and security checks. You should have your boarding passes when you check in for the trans-atlantic flight, or else you should be able to get them as soon as you arrive in LHR. Even if you don't leave the airport, I suggest you check your luggage. It will be much pleasanter to hang around LHR without the bags.

Chani,
I knew I would never make in all the way into London. I was just hoping that there would be a cute little village, 10 minutes away from the airport (by tube of course, ha ha). I guess I will just get my fish and chips someplace in the airport!

You could have a good lunch at a pub in Windsor and even visit the castle. A taxi ride from Heathrow will take 20 minutes and a local bus will take under an hour.

I agree with Tim, Windsor would be good. You really don't want to try getting to Chiswick !

Cynthia, Actually, there is something that meets your requirement of a cute little village with good British food near to Heathrow: the Ostrich at Colnbrook. http://www.theostrichcolnbrook.co.uk/ Colnbrook is a beautiful well-preserved village with medieval buildings about 5-10 minutes by taxi from Heathrow (check it out on Google Maps). The Ostrich is a "gastro pub" pub with good food, and we enjoyed it very much each time we visited. They have a range of local beers and a decent wine list. You could book a table through www.toptable.com, as it is popular and gets busy. I have lived in both Chiswick and Windsor. Chiswick is furthest away, though easier to do from Heathrow than Nigel suggests, as you have to know the trick: get off the Piccadilly line at Acton Town and take a taxi to any of the restaurants in Chiswick. Windsor is a taxi ride and is more expensive (further away from Heathrow than Colnbrook), but also charming and you can find good food there, and walk around the town. I agree with the others that you should simply check your bags through to Milan. Without them, it'll be 30-60 minutes from arrival to getting into a taxi or onto a train. You only need to be at the airport 2 hours ahead for a European flight, so be back at Heathrow for 3pm. That gives you about 3 hours. For my money, I'd have a slow lunch at the Ostrich... Mathew

My parents and I ate at "The Giraffe" I think it is called. Well, there is a giant giraffe in the restaraunt, you can't miss it. Excellent food and great service. It is located inside Heathrow.

Also Heathrow has 5 terminals and they are spread out as well!