I think your confidence is going to bite you on the arse!!
Just because you have 14 years experience from/in another country (which you don't seem to want to share) doesn't mean you are competent to undertake working in the UK. You will find that BS7671 isn't something you can pick-up overnight, and seeing as you will be expected to conduct any installation work in the UK to those regulations!! It would seem prudent, to be at least a little conversant with them don't you think??
Anyway, you go ahead and sit what ever exam you think you need without any training, and we'll all watch you fail. And you WILL fail, no matter how good you Think you are, because most of those questions will be based on and around that BS7671, which it seems you know nothing of!!