I'm assuming your Advance Parole/H1B/L1 is expired (correct me if I'm wrong). So your I-485 is no longer valid*, but the I-140 should still be alive if the employer did what was necessary to keep it alive by responding to USCIS inquiries if/when necessary.
So you can still get a green card either by filing I-824 to transfer the case to a consulate in the UK, or by entering the US with a visa** and refiling I-485 based on the old I-140.
* Your old I-485 might still be listed as valid in USCIS systems, if somebody at USCIS hasn't yet made the connection between your departure and the I-485 and followed the relevant processes to cancel your I-485. But the I-485 will be canceled later once they put all the facts together, so you can't use it. If you refile the I-485, you should first officially withdraw the old I-485 to reduce the possibility of mixups.
** You cannot file I-485 for an employment-based case if your last entry to the US was with the visa waiver, so you will need an actual visa if you're going to file another I-485. Preferably something other than a tourist visa, as it's also problematic (albeit not an outright ban) to file an employment-based I-485 when on a tourist visa.
