Only getting lukewarm water for a few mins

Hi, I am having issues with my boiler / timer switch, I'm not sure which at this point.

Basically the problem seems to have occurred when I tried to set a program via the timer



When I woke up in the morning I had no hot water so I tried to use the manual mode but again I got no hot water (this is how I normally use the timer rather than having it programmed).

I therefore reset the timer and tried the manual on setting again but again I got no hot water.

This then led to to look at the boiler which wasn't indicating any faults, I therefore decided to try out the active boost as I thought this would bypass the timer switch (I could be wrong) but again I got some lukewarm water for a few minutes and then nothing.

I have tried turning everything on and off again but I had similar problems. I am not an electrician but don't mind taking a quick look underneath if there is something I can check in terms of settings.

Any help would be greatly appreciated as I'm trying to avoid getting an electrician out during this pandemic and also for financial reasons.

Many thanks