Hows Buxton doing? A few years spent there in the 80's.
Unhelpfully, it depends on what course you are attending - most centres will issue a 'kit list' with their correspondence.
If they have already issued a manual - that's the most commonly forgotten item.
Then pens, note paper etc for study side.
Any relevant documentation - FAC, insurance ( and/or membership something like BASC, SGA etc ), if no FAC some form of identification.
Depending on location and set up outdoor clothing, boots and so on - carry warm stuff in case there's much standing about.
To take shooting test - rifle, bolt, mag, ammo if using own. Ear defenders - even if moderated. Sticks etc
Safety test - binoculars are handy
Most centres have spare kit to help you through. Generally advise people not to buy anything just for the course - as you'll see lots of kit there and may well change ideas in the process. But if you have stuff you are used to and like, thats usually better than borrowed.
Just a quickie rather than my usual drone on, but any queries, please dont hesitate to drop me a line.