Wall switches to switch off heater

So I moved into a rented flat last year, which has a PC2000, but have no idea what the wall switches are for (nor does the letting agents or landlord).

There are 3 switches on the wall for the PC2000.
The first on the left hand side says BOTT 1MM and is just a typical on/off switch, and is switched off
The middle is an on/off switch with a fuse, and is always switched on
The third, on the right hand side says TOP 1MM, and 'water heater', is a normal on/off swtich, and is always switched on - the previous tenants left a note on this one saying do not switch off.

I work away quite alot, and think it is a waste of money constantly having hot water, plus my electricy bills are quite a bit for 1 person in a 2 bed flat who is not often there, quite tight when it comes to bills, and put it down to this heater.

So any pointers would be appreciated.

I am on a single rate tariff

It should be on E 7 or E 10

If not costs more.

Keep it hot. If you use hot water then replace it.

When hot the unit will lose some heat but not a lot.

Check that the unit heats up and stops.
A faulty rod stat etc could over heat the unit. But rare

As for switches.

One is the supply to run the unit as in PCB and pump.
Leave on all the time.

The others are On peak heater (top one)

And Off peak heater (bottom one)

As you are not on E7 then heat the unit .

Could fit a timer to switch it on / off 2 hours before your DHW needs

Mike