Pharmacy layer (£40): ibuprofen + paracetamol (stock BIG bottles), aspirin (heart), loratadine/diphenhydramine (allergy/sleep), loperamide + oral rehydration salts (diarrhoea is a top killer when water goes bad — or DIY ORS: 6 tsp sugar + ½ tsp salt per litre), hydrocortisone, antifungal cream, laxative, antacid, cough meds, burn gel, electrolyte powder, 3+ months of every family prescription (ask your doctor for an emergency supply; many will).
Knowledge over kit: take a first-aid/Stop-the-Bleed course now (£0-50); store Where There Is No Doctor + Where There Is No Dentist (free legal PDFs — bundle them into the app and print them).
Sanitation — the unglamorous life-saver
Twin-bucket toilet (£25): two 5-gal buckets + snap-on toilet seat lid + sawdust/dry leaves/shredded paper as cover material. Separate wee (dilute 1:10 = garden fertiliser) from poo (cover every use, seal, compost 1 yr+ away from water, or bury 60 m from any water source, 20 cm deep).
Stock: bleach (also water treatment), bar soap (LOTS — cheapest disease prevention ever), toilet paper + the knowledge you can wash instead, bin bags (100s — waste, waterproofing, ponchos, solar showers), rubber gloves, wash basin, clothesline + washboard/plunger-in-bucket "washing machine."
Handwashing station: jug with a nail-hole tap + soap on a string. Cholera and dysentery follow disasters because people skip exactly this.
Solar shower bag (£10-15): black bag in the sun = hot water.