Hot water tank pipe to taps luke warm

[dilalio]

Lots of cylinder stat bits on the floor in first photo! So, fair bit of messing about been going on.

If components are wired and connected properly... Mainly heat going through coil for long enough and cylinder stat properly seated on "clean" surface of cylinder to detect internal temp as accurately as possible, then it may be that the coil is furred up and not exchanging heat to surrounding water.

 

[dilalio]

Edit: Double post... Think caused by @Madrab replying at exactly same time as me

 

[Nige F]

The immersion could be taken out - then you'll see the condition of the coil through t'hole.