They certainly are still valid. Any changes (and there haven’t been any recently) are updated in the course notes. So you can use the lectures and notes with a great degree of confidence … so long as you also spend hours and hours with a revision kit (from one of the approved publishers) practicing answering exam standard questions.
And, of course, when you hit a brick wall of lack of understanding anything, you can post on this page and I shall get back to you.