How many of them have you done to know you're not into them? I struggle with horror and walkthrough attractions too, but I think you should just bite the bullet and get the (not particularly frightening) DBGT over with next time you're at Thorpe. Haunted attractions are often some of the most creative and beautifully themed in the industry, and they're becoming ever more prevalent, so as a young enthusiast, it'd be easier at this stage to adjust to them. Of course, it'll probably help your cause in a few years when you're old enough to sink a few pints before heading in. Remember... They're not real!
I've definitely done something similar somewhere, but I can't remember where.
Also, I kind of don't really like the idea of actors getting all up close and touching me and all that kind of thing. I know it sounds very touchy, but I don't really like the idea of someone jumping all over me and in my face and whatnot; that kind of thing isn't my personal idea of fun, and fun is a big part of the reason we go to theme parks, isn't it?
For example, in the Scarefest topics, I've read about some of what happens in some of Alton's scaremazes, and I don't like the sound of that at all, personally!
On a random note, I just remembered where I've experienced actors in the past, and it wasn't in an attraction per se. Basically, we were in London once, and our hotel was in County Hall. To get to our hotel, we had to walk by what you guys probably know as the end of London with all the Merlin attractions (e.g. London Eye, Aquarium) in it. At the time we were walking, there was an attraction in this area called Fright Club that had scare actors roaming outside it that came up to us and jumped at us for a bit, kind of like what happens in a scare zone. I was not a fan of that at all, so that is part of what's put me off attractions with actors.
I know it sounds stupid because enthusiasts are supposed to be impervious to everything in theme parks fear-wise, but that's why these sorts of attractions don't really appeal to me.
P.S. Sorry for the long, off-topic post.