We did use the key to get in. Alarm them went off for a short period.
Guy did some checks on the car battery, and then put a booster on it, and we got the car started. He did more checks with voltmeter etc on the battery, and diagnosed the car battery was at fault (age unknown as it was in the car when I bought it, but it was a Halfords battery).
Once he'd changed it for a new battery (Bosch, 5 year warranty blah blah), we could unlock and lock the car again and all was OK once more. It was 8pm, Halfords was closed, and I needed to get back up the M40, so was just glad I was able to get back into the car.
I had literally been in and out of the car loading stuff in about 5 or 6 times, locking and unlocking the car each time when I went back into the house for more stuff. Then the last time I came out, pressing remote buttons did nothing.......
I obviously didn't have the second fob with me to try, but I was concerned perhaps the circuit board or the button contacts etc were worn out.