What if I dont need to take my exam?

There is an S1 exam and and English Literature Exam that I have been entered for, to be sat tomorrow and on Friday respectively. Both are resits and I have now acquired the grades that I want from each subject and see no point in sitting those exams. As well as this I havent revised for them so wouldn't get a good grade anyway.

1) What will happen if I dont go?
2) Will the marks I gained for them last year be used for calculating my overall grade or the marks I get IF I sit them this week.
3) If I dont sit them, or get a low grade in them (lower than what I got last year) will my firm and insurance Universities on UCAS find out? Will they drop their offers? (Having done some calculations I believe I have already achieved the grades that they asked for)

4) Will all my resits for a module be visible on my certificate for that subject?

These are a fair few questions so any help would be much appreciated!