I flew to LGW and back recently with a 4oz contact lens solution bottle. I kept it outside the Ziploc and hand it to the screeners each time. I didn't have any problems in any of the 5 checkpoints that I had to go through (in the way there, I got checked at the concourse, then at the gate; in the way back, at the concourse, the gate, and then again when connecting domestically).

I flew SFO-DFW-LGW with AA