What Monkey2001 said, but I would add to that. You would need to contact Liverpool to be sure, but most of the universities are running their waitlists on the basis that they will only offer to someone who doesn't have another offer of any kind. I believe there are poaching issues that they are concerned about (and that might apply even for a non medical offer). I think it is HYMS who has specifically asked for consent from those on the waitlist to approach them even if they have another offer, but I haven't heard of any others doing this.
I believe that to go into clearing you need to reject your other offers, but you could do that at the time. However given that all medical schools require interview, even when they go into clearing, I don't know how one would time it.
The advice universally is, if you are serious about medicine, take a gap year and give it another shot. You will be a year older, more mature, hopefully have more work experience etc (you can use the gap year to get this and many get a job and earn some money while doing it - working as an HCA is a common choice, you apparently really get to see what is going on in a hospital), more able to concentrate on UCAT/BMAT/Interview prep without the distraction of A Levels.