I know people have reported problems with using LH lounges when the onset of the trip is 4U...but what about if it is the last leg?

I am looking at either EWR-LHR-TXL or EWR-CDG-TXL where the flights to TXL are on 4U. The connection at LHR is about 4 hours and 1:45 at CDG. While doable it may be pushing it at CDG (not sure which terminal 4U is out of, assuming still the LH satellite?) and while I want to check out the new LHR lounge I don't want to have a 4 hour lay over and be sitting around the airport. I would be arriving on UA and while I know that UA operates the LHR lounge, I guess technically they don't have to/might not extend arrival access?