OK, so you meter has a separate live for the "off peak" and for the "24 hour" supplies. Observe that one of the grey cables has two orange identifying bands on it, and one has three. With luck they will be marked again on the other side of that wall, where perhaps they connect into your two consumer units. Possibly something is written on the bands.
It's probable that one of those cables is only live during the off-peak hours specified in your tariff (could be anywhere between 7 and ten hours, sometimes more). If this is so, you don't need to turn off your storage heater or your off-peak water heater (except maybe in summer, but the storage heaters should have a control panel, perhaps behind a window, top right front). Where you have neon indicators on the off-peak devices, you may observe they automatically come on round about 11pm or midnight. As electricity during these periods is half price, it's a good time to use your tumbledrier, washing machine etc, or to have a bath, because the cylinder will be re-heated at low cost. Your installation is not suitable for an electric shower.
Your consumer units ought to have rectangular lids over the fuses, and the purpose of each circuit ought to be written on the appropriate panels of the lid. Though IMO it is very useful to write, with permanent marker, on a strip of white vinyl tape above the row of fuses.
BTW as you have actual fuses, they must not be pulled out or put back unless the main switch of their CU has been turned off.
Storage heaters and immersion heaters are usually 15Amp and the fuseholder blue. I see you have a 20Amp yellow one. I don't know what this is for. Possibly two smaller heaters. 20A fusewire is not generally available. Fuses very rarely blow so it probably won't matter. MCBs to fit are obtainable, but opinions differ on whether that is worthwhile, or if it is better to fit a whole new CU at greater cost. I would guess your consumer units are somewhere around 1980's build.
Red is for 30Amp, usually Socket circuits or cookers. White is 5A, usually for lighting circuits. They are sized and shaped so they are not interchangeable. It's useful to keep a card of fusewire handy, there may be one hanging on the wall. They should last a lifetime.