Time taken for immersion to heat up

I'm renting in block 5.
The original Grasslin immersion timer switch was recently replaced with a Horstman E7 switch.
This is on for 5 hours (no other option) overnight, and has the option of a manual boost.
One 10 min shower is taken in the morning, there is no hot water left in the evening :(

It takes about an hour to get any hot water in the taps in the evening.
Assuming there are standard immersions fitted in these apartments, does it take this long for water to heat in any other apartment?
QE7 Timer Replaced

Mine was replaced with another almost identical. The engineer explained that the backplate (the wall mounting) did not have plastic separators between the power contacts so there was a risk of arcing and resultant fire hazard.

Otherwise there should be no difference.

I have the water heating for two hours straight (5-7) in the early morning and another hour at 4pm and another at 6pm. There are three people using this regularly and there's always hot water. A fourth person uses it and the hot water runs out but there's more available in the evening.

So far as I know, the hot water calorifier has has two elements a short element that heats the water at the top of the unit only and a long element that heats all of the water. The 'boost' you a referring to (I think this is true anyway) only heats the top segment of water. Enough for a sink full - not quite enough for a shower and definitely not enough for a bath.

So forget about the 15/30/60 minutes button thingy.

You need the main clock to be on so that the Bath light is illuminated and heating the water for at least two hours. Sometimes the effect of water heating isn't apparent for a day or two but by the second day it should be piping hot.

If it's not hot still, I would assume that the larger element is not heating for some reason and so needs to be checked by electrician/plumber. Check with the menagement company - they might recommmend someone.

There's the elements inside the boiler, the clock on the wall and a thermostat on the surface of the boiler. One of these might be faulty.

Let us know how you get on.