Locking problem

I'm thinking this may be related to a failing keyfob battery on a 2003 FL1.

Recently I've had a few beeps from the dash upon unlocking the car. For the last two days the drivers door doesn't unlock by the fob but the other doors do however the drivers door does lock by the fob.

Is this a common battery issue?

That sounds like a failed door latch and unconnected to the low fob battery

As Td4van said. You have 2 issues, which are unconnected.
The beeps are telling you that the battery in the fob is low.

The unlock issue is likely due to the lock actuator in the driver's door failing.