This is what I tend to do when I clean the bathroom (I have ADHD which means time blindness and so it often goes quite a long time between cleans).
Wear some clothes I don't mind if they get stained. (Not 100% necessary but makes me feel better if I'm doing a big clean).
Bin bag - pick up all the rubbish. Empty containers, tissues, loo roll tubes etc. If I'm feeling especially green then I might collect the recyclables first and separate them. If not - everything in the black bin. Change bin bag in the bathroom bin and put the contents of the old one in the bin bag. Keep this bag here for now.
Laundry basket - collect all clothing, towels, bath mat, dump in basket. Remove from room.
Hoover - preferably a small handhend one - to get rid of the dust all over the floor. Makes the rest less frustrating.
Get a microfibre cloth or other cleaning utensil (e.g. disposable J-cloth or sponge.
Start with sink - as this tends to be the "cleanest" thing in the bathroom.
Take everything off the sink (toothbrushes, creams, soap etc) and put in a pile e.g. on a towel on the toilet lid. (Can now hoover dust + fluff off sink if practical)
Using warm water and some kind of surface spray (e.g. Dettol) wipe down the whole sink + taps etc.
Bring back the items that should live on the sink, wipe/clean them one by one with the warm water, dry and place where they should go.
Repeat process with any shelves/cabinet near the sink.
Repeat process with bath/shower, if cleaning those.
Get bowl to hold hot water, bring this down to floor level. Clean floor, using warm water + dettol spray again, going in a circle with the area around the toilet last. When cleaning area around floor, also do outside of toilet bowl. I might clean the bin and the toilet brush holder if these seem absolutely grim - probably in the bath, using the shower, to minimise the chance of any splatter (sorry!!!)
Last of all is the toilet itself, as it feels like the dirtiest object to me. You can just rinse your cloth etc really well, or you might want to replace it after doing some of the floors. But this is what I tend to do.
Open toilet and spray the rim and underside of seat with dettol. Put seat down, spray seat + underside of lid, put lid down, spray top of lid (and the back of the pan). Run hot water in sink, rinse out cloth, wipe toilet lid. Open lid, wipe underneath lid and on seat, open seat, wipe under seat and around rim. (Rinse cloth as needed during this).
Place cleaning cloth into the bowl used earlier or in the bin bag if throwing away.
Drain water in sink and run an extra sinkful to swish around with hands to rinse any germs from toilet cleaning.
Last of all, use toilet brush to push as much water past the U-bend as possible. Now get your Harpic and squirt under the rim and all around the bowl. Close toilet, wash hands and leave the bathroom. Throw away the rubbish, take cleaning cloth in its little bowl to washing machine and wash at 60C or higher (can do with towels, bedding, etc, or just empty as a cleaning cycle).
At least 20 mins later but as long as possible, go back to loo and scrub the harpic with the toilet brush, as much elbow grease as you can manage, then flush. Replace bath mat, towels with clean ones.
If you have very thick limescale in toilet you might not be able to clear it using this method - you need some kind of strong acid to dissolve it. Don't mix different bathroom cleaning chemicals, especially bleach. You can try vinegar overnight in the toilet bowl - you might need to repeat a few times if it's very thick. It will smell absolutely terrible as the urine, bacteria etc seep into the limescale and then get released, but once you've cleared it once it's easier to keep on top of it.