One rabbit holes to stay well away from is getting too giddy about timbers and ending up with lots of random boards of different species. You'll never have enough of one type to actually make anything, and the learning from working with one timber can sometimes run contrary to best practise with another timber.
For a UK woodworker I'd suggest sticking to just two or three different timbers. If you have material left over from one project it's easy to then use it up in a future project, this gives you the incentive to sensibly
over buy which is a smart strategy. Sticking to just a few species also allows you to build up stocks in different
thicknesses, you'll find this invaluable later on in your woodworking career.
Once you're past the Pine/Tulipwood initial learning stage, and are ready to start on real projects, then I'd suggest picking from the following, and whenever you're in a timber yard and see some more of your chosen woods offering good quality at acceptable prices then grab the chance and add some more boards to your stocks.
American Cherry. It patinates beautifully and quickly, standing up well to sunny interiors without fading. It's also ideal for the Shaker style furniture that's both popular and appropriate for beginning woodworkers. Cherry is kind to your tools, easy to glue and fasten, reasonably stable, and reasonably homogenous from one tree to another.
Oak. Not American Red Oak, but European Oak. You can't be a British woodworker without getting to grips with this national treasure. Plus it's so hard and strong that you'll always need some Oak for stuff like drawer runners which are subject to wear.
Sycamore or Maple. They're closely related species and can be used interchangeably. If you need a pale timber with a fine grain then these fit the bill. Just be careful when buying Sycamore to make sure it's clean and white (sometimes called Arctic Sycamore), it's not an expensive hardwood but if you chase a bargain you're likely to end up with horrible grey Sycamore that has ugly sticker marks.
Douglas Fir. Not the normal crepe stuff in builders yards, but the quarter sawn, knot free stuff that's fast becoming the go-to timber for environmentally conscious furniture makers. If you want to get ahead of the fashion curve this is one to explore.
Avoid dabbling with non commercial and hard to source timbers, leave stuff like Laburnum or Brown Oak or Swiss Pear well alone until you've built up a network of timber yards and have some experience under your belt.
You'll find more tips and information here,
how-to-buy-hardwoods-t107912.html