Range Tribune HE hot water problem

[dj81]

Just asking for advice on here before I get in touch with the landlord, but I've been having a problem over the last week with my boiler (a Range Tribune HE).

I have it set to come on between 5-6:30 every morning, and this has been the same for months. It has always given me enough hot water to last the day, even if I was to have a shower and a bath.

However, the other day I got home from work to find the water was running lukewarm, and quickly went cold. I put the boost on just to give me enough hot water for the rest of the day. The following two days, the shower was hot and in the evening there was plenty of hot water from the taps, so I assumed whatever the problem was had resolved itself.

But apparently not. Today I got home from work and the water was stone cold. Not even a hint of warmth. The timer is working fine and the shower this morning was hot, so I really have no idea what the actual problem is here. Especially as it seemed to rectify itself for a couple of days. I have not changed anything with the boiler or timer and have not been using any more water than usual.

Has anyone got any ideas as to why this is happening?

 

[McCombi]

Unless you shower very quickly I don't think just having it on 1.5 hours in morning is enough for a shower and a bath.
What size of cylinder is it?
How many people using it?
Clock on timer set correctly after clocks changed few weeks ago?
Definitely got the programme times correct?