Can anyone point me in the right direction as to what's actually happening to my tree here? Upon inspection of the roots I don't spot anything alarmingly unusual?

Breathnez - thank you for your response, did your tree look anything similar to mine at any point?

I would definitely do what breathnez and re-pot your ficus in some well draining compost as the compost it is in looks well past its best.

I was just wondering about the pot it is in. Is it in the pot it was sold in as sometimes they are just sold to look good on the store shelf rather than be good for the plant.

Is that a separate drip tray on the bottom of the pot or is it attached to the pot?

No, it never showed that white discoloration. I cannot tell if that is hard water staining or mold, but either way it looks like too wet too long.

the whitening is from your lime hard water use rain water if possible. it just stain and it doe no harm to your plant on the bad side it only make it look bad.

None-the-less, the bark must be wet enough, long enough, with enough evaporation to leave behind that much mineral (if that's what it is). Needs to be in a much faster-draining substrate.

It makes perfect sense as I have only ever used hard water, I shall use rain water captured in our water butt from now on - thank you! I shall also repot him, in a succulent mixture.

Gareth - the pot isn't attached to the white unit, the water drains into the white unit through pours in the bottom of the inner pot (black).

In all fairness I have probably provided a little too much water, although not too frequently, but it'll still have the same detrimental effect I presume.

In terms of mixture to repot into, I'm relatively inexperienced and would appreciate any suggestions in terms of brands and feed etc.

search 'gritty mix' on this site, will give you a lot on succulent mixes.