I wouldn't be buying a car that didn't have two things that I really wanted, and especially not from someone who doesn't know how big 5" actually is: His missus must be so disappointed. Also mismatched tyres, And The Use Of Caps For Every Word Is Quite Irritating. Still, if you're already decided on it then I'm not sure what use our opinions are.
Leather retrim will be from about £600+ I would expect depending on what you want and where you go, Brembos are easy to pick up from someone like Zmanalex on here. That said, do the Brembos even fit a 17" wheel? I don't know, genuine question.