It's understandable that you are finding it difficult to find what you want on Adobes labyrinthine site, but this should be the correct page;
The third item down is LR and you can order from there.
It is even more contorted than that:
On the page you linked to above, you have to click on the tiny link in the box on the right (headed Creative Cloud) that says 'student and teacher pricing'. That takes you to a page where a selection of software is displayed. To get to LR you have to click on the dropdown above that says 'view all student/teacher products.' Only THEN can you see the standalone LR at the student/teacher price of £57!
I love Adobe products but I really detest this kind of manipulation. Obviously they would prefer me to subscribe to Creative Cloud, but they have made the standalone available for people like me who have invested recently in standalone products. The least they can do is make that availability apparent.
I was only able to find the product with help from Adobe on their Chat facility. That worked well, and the rep knew exactly where to send me, which is something.