Mira Combiflow - Built-in

A: Check that shower hose is not kinked or collaosed internally and head is clear.
Check that filters are clear.
If the boiler has not been serviced recently it may be worth having it checked.
If all above are ok then it is probably the cartridge at fault and areplacement can be ordered online via the link below which also shows an exploded diagram of the unit.

http://www.showerdoc.com/shower-spares/mira/MIRA-PARENT-29-Mira-Combiflow---Built-in

A: If you can access the supply pipe check that hot water is reaching the valve, if not it may be a boiler problem.
If hot supply ok then it is probably the cartridge at fault and replacement can be ordered online by clicking on the link below.

http://www.showerdoc.com/shower-spares/mira/MIRA-459-07-Mira-Pressure-Balancing-Cartridge-459-07

A: The Combi Flow is a non thermostatic mixing valve and will not alter temp of water. This is a fairly common problem and is caused by the boiler " cycling " therefore would recommend you have the boiler checked.