From the photo, may I suggest the following possibility.
Could well be that the plastic ‘pod’ is held in place by hidden nuts located behind the control knobs and the fixed shower head at the top, plus the use of mastic around the joint between the pod and the tiling. If there is no mastic around the joint to the tiling, then in all probability the plastic cover is a snap-on fit to some sort of base plate.
The center plates of the control knobs (metal or plastic) are probably a push on fit, in which case they can be levered out by the simultaneous use of two very small screwdrivers positioned opposite each other. Removing the center plate will probably reveal a central screw or nut of some type, which when removed, will allow you to pull the knobs off the spindle. Often there is then a screw on shroud which can be removed (use mole grips or similar) to reveal the metal nut that is holding the pod in place.
Spraying the whole assembly with some proprietory decalcifying product, and allowing it time to work, will make the disassembly easier if it has been in place for a long time.
There may well be a similar process to follow for the fixed shower head, in that the parts will progressively unscrew until the all important retaining nut is revealed.
With the nuts removed, and the mastic cut through with a Stanley Knife or similar, possibly the whole unit, or more likely the cover, should then pull off the tap and shower head spindles towards you.
Once you have sight of the interior connections it should be fairly plain sailing to see what needs to be done to get the rest of the thing off the wall.
It’s a good idea to have a set of small Allen (Hex) keys to hand as sometimes there are small grub screws to be removed in order to get some of the parts off the tap spindles. The grub screws can be difficult to spot if they are all gummed up with calcium deposits.
BTW — Don’t forget to turn the water off before you start. Sounds obvious but I think we have all forgotten something basic like that from time to time. Myself included.
If the pod has been in place for a very long time, and a combination of decalcifier and WD40 doesn’t work, then it may well be that you will have to do some damage to the pod in order to remove it. At that stage a small angle grinder comes in very handy. Brutal, but effective.
It will also be a good idea to fit some isolating taps (at the earliest possible stage in your endeavours) to the water feed pipes if they are not already present and functioning. This will save having to have the entire water supply to the house turned off during the work.
I don’t wish to “teach Granny to suck eggs”, but having all the required bits and pieces to hand before you start may well prevent a lot of inconvenience.
Good luck, and please do let us all know how it pans out.