2013 1.6 TDI. Original battery

Monday, drove 200 miles. On reaching destination, car would not lock using the fob. Fob light was working. Drove back home same day. Again, would not lock, used the drivers door emergency lock.

Bought new fob battery.

Today, would not unlock using the fob. Unlocked it maually. Started normally, that's when I noticed a few things.

No interior lights, very faint display on main entertainment screen & the MFD. No front side lights, no daytime driving lights. When I turn on the headlights, they come on, but when I select main beam, the blue warning light comes on but no main beam.

Front windows not working, rears ok. Brake pad warning light came on. Passenger door won't unlock

Drove in normal London traffic for a couple of hours, a/c working normally as well as s/s. Had to lock it manually but only the drivers door is locking.

It all points to a battery problem, but if that was the case I wouldn't expect s/s to work.

I don't have a code reader.

I was thinking of disconnecting the battery to see if the system would re-set itself before getting a garage involved

Before Monday's trip it had been standing for about six weeks.

Any advice please?

Very odd that the SS is still working, but strongly suggest a proper load test on the battery.