Lost heat in my Gravity Shower

[afeliciello]

I seem to be having continual problems with my gravity shower.

First, I used to lose pressure. Taking the shower head off and then leaving the shower running with the shower hose left lose in the shower tray sorted it.

Now, I have another problem, my shower is always cold.
If I take the shower head and move it to a much lower level, i.e. by my knees, it gets warm again. Generally, I have the shower mixer on level 6, it is now on 9.
I have a sink next to my shower and the hot water there is fine.

Any ideas?

 

[MANDATE]

My thoughts are that the desired temperture is obtained by mixing cold water with hot water.
Now in cold weather the cold water is a few degrees colder so that could be a factor.

Also if you have a combi boiler, could the boiler tubes be furring up slightly and the 'hot' not reaching the same temperture as previous.?
Has the mixer got any adjustment valves to regulate the flow.?
If you have isolation valves can you not close the cold slightly so you get less cold water mixing with the hot.?
Is there a filter that needs cleaning.?
Have you recently turned the boiler stat to a lower temperture.?
Is the cold water under mains pressure?
If the hot water is restricted by your shower head it will alter the ratio of HOT to COLD. ie less hot water is the same as more cold, perhaps it just needs cleaning out