Whether you need an ETA or not to enter (UK or non-UK citizen), as far as United is concerned, you are a Polaris customer whose flight terminates at Terminal 2, LHR. You are not connecting. You hold two totally separate tickets, one terminating at LHR, and a second ticket originating at LHR. I don't see a reason why you can't do what you want to do. Pick up your bag, clear C & I, check in at the Icelandair desk to check your bag. Then go back to the Arrivals Lounge for whatever time you can before heading for your flight to KEF.

In many airports, there is a buffer zone after you clear immigration, pick up your checked bag and clear customs. Technically you are in the country but it is not open to the general public - a good example is the bag recheck area after customs in the US - people meeting someone arriving on an international flight are not allowed in this area. I have come across similar zones in other countries - once you exit through the double doors, you cannot re enter that specific area.
So, my concern was, exiting the customs area and finding myself in a similar zone where the Polaris Arrivals lounge is. By leaving it to go and check my bag at the Icelandair counter, I could find myself unable to return to that particular section of the airport.
I am aware that United doesn't care about my flight with Icelandair & will recognize me as an arriving Polaris passenger, I just want to make sure I can enter that area again after I've checked my bag.

You would need an answer from someone with more knowledge regarding LHR T2 to ease your anxiety, but I would figure once you are landside, you can go anywhere you need to. The UA/AC Arrivals Lounge is landside. So is Icelandair check-in. Just two different levels. I don't see a reason you can't take an elevator up to Level 5, check-in to KEF, then come back down to Level 1 and enter the lounge.

Just a note that this is not a “Polaris Arrivals Lounge”. It is just signed “Arrivals Lounge” rather generically, and has some Heathrow signs to the side that say United and Air Canada.

Wanted to point that out so that you weren’t looking for Polaris branding. But the lounge is right outside arrivals to your left, and there should be no issue doing what you want to do.

Yes, as soon as you come out of Customs and into the Arrivals Hall walk straight ahead and take either the elevators or escalators up to Level 5 / Departures. Icelandair is Zone C checkin, which is on the same side as United. You�ll be able to check your bag in, then take the escalator or Elevator directly back down to Level 1 on the same side. Then go straight into the Arrivals Lounge.

There are no access restrictions Landside once you pass through Customs.

The Arrivals Lounge closes at 2pm sharp and they are strict!

You will be leaving the secure area after immigration and customs. The arrivals lounge (it�s not a Polaris Lounge) is immediately to left as you exit into the public area. There is no need to immediately check bags if you don�t want to. The arrivals lounge expects people to have luggage with them.

yes, you can go up to check in then back down to arrivals

As of today (9/15) -- Hand Sanitizer and roses....

Time apparently waits for no one.

David

Speaking of time - UA in LHR has pre boarding for pre boarding - it actually works out quite well and they monitor it well. They have the room to do it - wouldn�t work at any of United�s hubs�..

LHR Arrivals lounge is pleasant but not luxurious. As noted above it is outside of security so you'll have to go through that process to get to your connector.
The shower stalls are great after a red eye but there can be a bit of a line on the sign-up sheet. It reminds me of the Plumeria lounge in HNL (unfortunately no longer a Priority Pass Lounge).

WHYYYY???

Agreed, lots of people leave their large checked bags behind the counter (I think there's a closet) while they shower and have breakfast. So unless the poster is tight on time for the onward flight baggage cutoff, this would be more efficient then going upstairs and back down (and then back up).

Separate note, the food offering on the buffet is pretty decent (lots of smoothies, fruit, pastries, yogurt/muesli), but do avail yourself of the made-to-order items from the kitchen as well -- full English, usually something with smoked salmon, sometimes avocado toast. You'll have to proactively flag down one of the servers to order, but this is what elevates the lounge from decent to very nice and many people don't realize.

+1 -- it's not a luxurious environment at all -- more like a cafeteria, good food and nice showers which feel great after a short red eye that I always take... Unfortunately there was a rail strike in the UK last week so I did not have enough time to use the lounge after my flight...

My apologies if this was discussed previously. I�m currently in the arrival lounge at LHR. A cricket match was on the TV and no one was watching it. I asked if they could change the channel to BBC to catch up on the news. I was told that this was not allowed and had been the policy for about a year. I asked why and was basically told that it was not politically correct. Apparently there had been complaints by some patrons that the news was offensive. My word. Any thoughts?