Checked with a few friends, none of them have ever been asked to actually show their certificates at an interview, certainly I have never been asked for mine. Small wonder that some people have been hired on the basis of qualifications which they never achieved!
Best bet is to run around finding certificates if asked for them. I don't think that you will be asked, in any event, whilst not wishing to devalue A level achievements, I really don't think that A level certificates are all that relevent or important in the scheme of things. An FATPL is more likely to be what an employer will focus upon and what you will be required to present.