Don't worry man , All the companies are already set up actually even before you contact any acountancy firm . They just put you as a director in one of them . Once you've signed the accountancy contract it's just a matters of hours to get this done .
I was a bit nervous about this as well and honnestly if you want an advice , just fill up all the documents they ask for , send them back all the stuff and they ll take care of all .
The most interesting part is for the St james security check , Good luck