A: It sounds like your TCO ( Thermal Cut Out ) has gone faulty and that means you would only get cold water coming through the shower.

In some cases it can be just the TCO that has failed but in other cases you could have a problem with lack of water pressure or a fault with the flow valve causing the shower to keep overheating and taking out the TCO.

The part number reqiured is 416.41 in the link provided - http://www.showerdoc.com/MIRA-416-41-Thermal-Switch?ss=416-41
Answered 170 days ago | Showerdoc

A: 

The things to check first are.

1 That the main valve coming into your house is fully open.

2 Then check that the valve on the line to the shower is fully open.

If these valves are not fully open then there may not be enough water
getting to your shower to cool it.

Also check that the shower is connected to the water mains and that the mains pressure is at least 1bar.

If all the above are OK then you may need a new flow valve.

Here is the link.

http://www.showerdoc.com/shower-spares/mira/MIRA-1563-508-Flow-Valve-Assembly-10-8-kW

Answered 71 days ago | The Doc

A: 

The things to check first are.

1 That the main valve coming into your house is fully open.

2 Then check that the valve on the line to the shower is fully open.

If these valves are not fully open then there may not be enough water
getting to your shower to cool it properly the overheat safety device will turn
the power off until it cools Then it all starts again

Make sure that the shower head is clean and clear, that the hose isn’t kinked (this can happen just behind the hand set where it is difficult to see) also check the inside of the hose although it can look OK on the outside it could have collapsed internally

If all of these are OK then you need a new flow valve

Here is the Link.

http://www.showerdoc.com/shower-spares/mira/electric-showers/MIRA-1563-508-Flow-Valve-Assembly-10-8-kW

Answered 60 days ago | The Doc