A hiking first aid kit does not need to be big, but it should be useful. Many shop-bought kits contain things you may never use and miss items that actually matter on UK walks. The best kit is small enough to carry every time and practical enough to deal with common problems.
Blister treatment should be near the top of the list. Blisters are one of the most common hiking issues. Carry blister plasters, tape or dressings you trust. Do not wait until a blister is fully formed. If you feel rubbing, stop and deal with it early.
Add a few sterile dressings for cuts and grazes. Wet rock, brambles, sharp stones and slips can all cause small wounds. Include antiseptic wipes or wound cleaning wipes, plus a small roll of tape to hold dressings in place.
Pain relief is useful, but carry only what you know you can safely take. Many hikers keep a few paracetamol or ibuprofen tablets in a waterproof pouch. If you have allergies or medical conditions, adjust the kit to suit you.
A small bandage is useful for sprains or support. You do not need a full medical bag for normal day hiking, but something that can wrap an ankle or secure a dressing is sensible.
Tweezers are handy for thorns, splinters and ticks. Tick removal is worth thinking about in grassy or wooded areas. A proper tick remover is small and light.
Include any personal medication. This is more important than generic first aid items. If you need an inhaler, antihistamines, insulin or other medication, make sure it is protected and accessible.
Keep the kit dry. Use a small dry bag or waterproof pouch. A wet first aid kit is not much use.
For longer or remote hikes, add an emergency blanket, whistle and a small note with emergency contact details. These are lightweight and can help if something more serious happens.
The point is not to carry a hospital. It is to handle the likely problems: blisters, small cuts, aches, ticks and minor injuries. Build the kit around your walks, then actually carry it.