With the loss of the 747s (and ensuing larger crowds in UC due to loss of GF), maybe there may be some more Surprise and Delight invitations for 1Ks in J?

More likely the GFLs will be closed / converted -- such as it has been reported the SFO GFL is converting to an UC in early October 2017

Winter of Crappy Lounge Experiences is coming...
(or Crappier)

Is the First Class side of the LHR United Club still open to GS flying on a business ticket?

.

Absolutely. No guests, however

I got invited to use the IAD GFL - a personal first. I asked at the C7 UC counter if there was any ETA for a Polaris lounge at Dulles, and once we finally got my boarding pass scanned on the third try (GPU cleared into BF with 24 hours to go), she handed me an invitation to go here instead. It is quite pleasant.

Just an update to add about the IAD GFL. Think old ORD FIL/GFL but without the views, different seating areas or any of the style/art elements of that old lounge (there are windows but they look out onto a hall (where people are boarding/exiting) and then windows to the outside. The main space is longish room with bunches of leather and cloth chairs with no dividers. It was quiet, Id estimate there weren't more than a dozen people during my evening visit. Across the hall from the main seating area is a desk that was staffed by two agents, restrooms, a small conference room and small work area with cubbies (no computers). There is no real style to the lounge which is a pity because it would seem UA could easily have placed some of the nicer furnishings from the now discontinued GFL in other locations (e.g. the Asian style from ORD or nicer chairs from SFO). Food offerings seemed minimal compared to old ORD GFL (what I was most familiar with).

A brief summary of beverages:
Very decent self-serve champagne: Laurent-Perrier Cuvee Rose and Moet & Chandon Imperial
Several red and white wines as well as bottled beers. White wine (on ice) included: Erath Pinot Gris, Kim Crawford Sauvignon Blanc and Rombauer Chardonnay
Typical range of spirits including bottles I havent seen in other business class lounges like Patron and The Balvenie DoubleWood 12
Illy Coffee Machine

The buffet menu:
Thai Chicken and Rice Soup
Chicken Fajitas
Dill Marinated Roasted Salmon
Vegetable Roll with Duck Sauce
Basmati Rice
Green Bean Almondine
Several cold salads including a Spinach Pesto Salad and Asian Noodle Salad as well as minimal cheese and fruit plates.
Desserts looked like a few packaged items (e.g. things I'd see in a frozen food aisle like mini lemon meringue tarts).

GS traveling in *A business class
 

United First Class lounge access at LHR
 

Yes, that entitles you to access.

Would also like to add that GFL access is inconstant. Was told at HKG that as a GS, my HKG-TPE-SFO ticket was ineligible because my TPE-SFO (UA J) had not started yet and that HKG-TPE was on BR so it was ineligible. My understanding was that access was available 24 and same day of departing Polaris biz. Was very confused and was told otherwise at SFO.

HKG