My 19 year old son changed his surname by Deed Poll. He included my surname after his and his late father's surname, which he also kept to keep his father's side of the family happy. The Deed Poll came through in time for his new name to be included on his BTEC Level 3 Extended Diploma. But his GCSE certificates will always have just his father's [i.e his old ] surname on them. For his Social Care college course and work placements he has to have an up to date AccessNI Enhanced Disclosure Certificate. But each year on the application for a new one they ask if he has been known by any other surname. Which he states that he has, and there is usually no hold up at all. This is for what they call Regulated Activity ,i.e. for working with children and vulnerable adults. I doubt it is going to matter for any other job.You will always have your Birth Certificate with your original name on it anyway. I think it is important that, even though you intend to change your name that you do so,as far as with a view to training or employment are concerned, in a completely open and honest way. Don't try and pretend you never had the name you now have. That would come across as being quite deceptive I think.