(Another) Key Fob frustration

My 'main' use key fob has been playing up for a few days, working fine some days, intermittently others, not at all (for locking, ignition fine) on other occasions.

I went for the standard 'clean the contacts & replace the battery' fix, the labelling inside the fob cover says 2025 but I seem to get more reliable performance from a 2032.

However, today regardless of which battery spec I try (2025/32/36) the car will not lock, either by the normal touching the handle or pressing the lock button on the fob. When I do press lock on the fob the red LED doesn't illuminate, but it does for open & open boot & these functions work as expected using the buttons.

With the spare it will open/close on the button & the LED flashes for all actions, but neither key will now work for keyless. 

Any help appreciated. Thanks.