Read the magazines and you will see the latest £500 waterproof jacket in every lurid shade, or an advert trying to convince you that you need an all-singing all-dancing GPS watch which will cost you half a month's wages. You probably won't see much focus on these simple but absolutely vital bits of kit, all of which will have a much greater impact on your safety & enjoyment than the latest gadget or fashion accessory.
There are loads of cheap alternatives to an Ortlieb case but none of them have the same high quality rubber! This matters because the compass has little rubber feet which stick like glue to the Ortlieb when you take a bearing. On cheaper cases the compass skids around. Silva are the only ones who come close with their Carry Dry map cases, but they have a bizarre zip type closure which is a bit of a nightmare to operate. The Ortlieb A5 size is my favourite since it fits nice and snug inside all jacket pockets. Don't forget to ditch the weird cord that comes as standard on Ortlieb cases - how can you keep the map set if it's round your neck? I prefer to attach my compass direct to the map case, or you could use the same cord to attach to your jacket pocket.
My standard smartphone GPS setup is Viewranger running on Android. Currently a Samsung S7 sitting inside a Lifeproof Fre, so the whole setup is completely waterproof and somewhat sturdier (though still fragile compared to a proprietary handheld GPS unit). You can easily attach a little lanyard so you can clip the phone inside your rucksack lid pocket - which is where it belongs right? That way there's no chance of the strong magnetic field from the speaker interfering with the polarity of my compass. I'll typically end a winter day out with battery life around 85%, having started fully charged. Sorry to all you Apple fiends out there, but I've seen so many times now that iPhone batteries are way less resistant to the cold. I can't offer any evidence for this, just repeated personal experience of Android phones outlasting Apple.
Compass-wise, the Silva Expedition 4 pictured above is currently the only choice that really makes sense in the UK, since no other quality compass has 1:25,000, 1:50,000 and 1:40,000 measuring scales. If you're not sure why this is important, check out Steve Fallon's excellent blog on UK mapping at this link.
Pictured to the right is the smaller Silva Ranger, which is ideal as a backup compass. On all but the most trivial hillwalks I will carry a spare map & compass tucked away down the back of my rucksack (where a water bladder is designed to go) with an identical setup to my main one. But Expedition 4 compasses are quite expensive at around £30, whereas you can get away with a cheaper smaller compass for half that.
One last detail is your timing card.
I have met people who are sufficiently adept at mental arithmetic to calculate, in bad weather and when tired, how long it should take to cover 350 metres at 5km/h, with 200 metres vertical ascent. I am not one of these people. Therefore I am never without my timings card. You can print off a free card from the very open-minded people at Lupine Adventure Cooperative - (click this link), or if you want something that'll last better you could pay a few pounds for this credit-card style example from the Shaven Raspberry shop run by navigation legend Lyle Brotherton (click this link).