Hi there and welcome to the forum.
The worst thing with kits like you have mentioned in your post, is the cost they charge for accumulating the tools. Two hundred & twenty five pounds seems quite high to me.
That Stanley knife might be OK, but they might have a ridiculous price on it when you buy it in the kit. You can buy a similar knife quite cheap in Australia, so I am assuming you can in the UK.
Some of the other speciality tools might be lower quality that bend, don't hold an edge or break easily. It's difficult to know without actually knowing the supplier and specifications of each tool or having seen this kit previously.
Personally, I would (if I could) make a trip to a supplier to get some ideas about leather types and suitability for which purpose, get some tools in your hands and ask questions about their uses.
As for your thought to make some small projects in the beginning, great idea. But you might fine that a dozen or 20 of an identical small project, (like a key fob to give as gifts to family and friends) will help you learn a lot.
After cutting out that many similar items, you will more about cutting leather. Then after stamping, edging, dyeing, you will know more about each process. Always save each piece, even if it has a mistake design alteration, because it can be handy for testing out the next process.