Been keeping bees since I was 12, now I'm 66 and still learning.
I certainly wouldn't go WBC - they are a complete pain to work with and although they look cute, I would never use one unless you are in the north of Scotland or similar. They are a double walled hive with an external shell (called "lifts") and internal boxes. They were designed back in the late 1800s for harsh winters we no longer have so you could pack straw between the outer and inner layers. There is absolutely no need for this in 99.9% of the UK. We have a couple of WBCs in our training apiary mainly to show new beekeepers why they should never consider a WBC.
I would stick with BS National designs as the equipment is far cheaper than other designs as it's by far the most popular on the UK for non commercial bee keepers.
I would however strongly recommend using either a "Commercial" or "Deep National" brood box.
The standard National brood box (and all the other older styles of brood boxes) were designed for a type of bee that we really don't have in the UK any more. The standard modern queens are far more fecund and lay around 2,000+ eggs a day in the height of the season with a colony size of 50,000+, far more that the bees we used to have. The older style small brood boxes rapidly get overcrowded which can lead to a host of issues, e.g. more frequent swarming. Deep national and Commercial boxes have much larger brood box volume which is better suited to modern bees, whilst still having the same cross-section (approx 46cm x 46cm) as the common BS National kit, so floors, queen excluders, supers (honey boxes), crown boards and roofs are available from loads of suppliers and relatively cheap due to competition. To get more space, some folk use a standard national brood box together with a super as the brood area, referred to as "brood-and-a-half" - do NOT be tempted to go this route - it's not only a poor compromise , it's a major pain as you never know where the queen is - just go for a single bigger brood box in the first place!
Also go for a flat roof, not a pointy one. With a flat roof you can put a lump of rock on it in the winter to keep the hive safe, plus, and most importantly, when going through a hive you take the roof off and invert it on the ground so it can be used as a stand for each bit as you take them off. Pointy roofs look pretty but are impractical.
If you can afford it, 100% go for Western Red Cedar. I have WRC hives that I made up 20 or 30 years ago and which are still in good condition. You can either leave them to go silver and weather naturally, or some folk use a water-based external finish such as Rustin's, which is bee-safe. All my hives are 100% WRC.
I've tried making my own hives - it's doable and satisfying, but largely pointless as you can buy decent flat pack ones for much the same money and far less hassle. The commercial suppliers have the advantage of buying cedar by the container load at pricing which individuals can't compete with. I now only repair my hives with bits of cedar which is increasingly difficult to find.
