Getzoo do some great platforms suitable for that kind of cage - but you wouldn't get one before Saturday! You could maybe add one later if you have a good house to start with. They do either corner ones or some racetrack type ones that go round two sides. As Ria says a platform is always a good thing - they seem to like running up onto a platform and sheltering under it (a favourite place for a wash maybe) or just to feel secure. It's also a good place to put heavier ceramic items. They do two heights - the 21cm height is better as it allows for plenty of substrate under it and still leave a gap between the substrate and the platform to sit under. You could use your cork log as a ramp up to it. I've done that a few times - just kind of wedge the log so it's part under the ramp and part sticking out in the cage - they can run through the log or climb up the side onto the ramp.
From your list:
1) I wouldn't use the coconut soil - especially in a tank style - risk of humidity and mould which can affect respiratory system - stick to the other substrates you have.
2) I'd get one of these - corner litter tray/potty
TRIXIE Corner Toilet, 16cm x 7cm x 12cm : Amazon.co.uk: Pet Supplies
3) I'm not sure about the sand you have. Reptile sand isn't always suitable. The tiny friends one is ok, or some people use children's play sand and bake it. I get this one:
JR Farm Chinchilla-Sand Special | zooplus.co.uk
Also agree with Ria - a large house/nesting box is an essential - either a shoebox house or you can buy some really good labyrinth houses from rodipet (but they're expensive and also wouldn't be there by Saturday). And have them on legs so they don't sink into the substrate.
Etagen | Einrichtung & Zubehor | Getzoo.de
Or you can make a platform using Ikea knuff magazine racks (but the hole needs blocking off).
knuff hamster shelf - Google Search
Or Trixie do this which is quite cheap - and might be there before Saturday
Trixie Natural Living Shelter, 30 x 22 x 25 cm : Amazon.co.uk: Pet Supplies
To me, the most important thing, after the basics of cage, substrate and wheel - is a large house/nesting box that's dark inside. The first thing a hamster wants to do is find a place to nest and feel settled. And build a large cosy nest and burrow down in the substrate and bury hoards under the nest. So it's best if it's open underneath and sat on the substrate. If it's large enough and you put a corner litter tray at the end opposite the door (the other end will be darker and they tend to nest at the darkest end) they will almost certainly use the toilet. Just put Chinchilla bathing sand in the toilet.
A new hamster may take a few weeks to get fully toilet trained and have the odd accident in the nest but they generally choose a place to pee away from the nest - in a corner - either the corner of a large house or the corner of a cage.
Then the cage stays clean and dry for a long time - you just take the top of the house and empty the litter tray once or twice a week.