Yeah, I'm a bit worried myself. It's a gamble.. that's all there is to it. You'll either get them or you won't.
Just to be prepared, I suggest for all of you to go to the UK Ticketmaster site, then register. It's free. Then, you can put in your billing address and credit card information. Why? Because this shortens the checkout process.
When you log into Ticketmaster for the sale, you'll want to do so early. Hit that refresh page every couple of seconds. As soon as tickets go on sale, choose your price and section (those of you wanting the best seats just leave everything as best available). Once this happens you will enter a security code. If that checks out and there are tickets, Ticketmaster puts these tickets on hold for you so you can type in your contact information. I think it holds the info for around two minutes. If you already have an account with your information saved, this takes mere seconds. Then, you choose how you want your tickets delivered and that's that. The reason I suggested an account is that if you're a slow typer or whatnot, there's a chance the tickets could be released if you don't type in your info fast enough. By creating an account and saving your info, one step is done.
Also, if you don't get tickets right away, it's worth staying on in case someone tried to get tickets but was unsuccessful. The tickets will be released back into the inventory and some lucky person will get them.
But yes, not trying to scare anyone, but the window of opportunity for purchasing these tickets will be seconds.