It shouldn't, but there are some colleges that are "less lenient" with gap year/deferred entry students. Some colleges are very happy to accept deferred entry applications while some would rather you didn't (however this is more applicable to courses like maths). However, your application should have equal weighting to other applications that aren't applying for deferred entry. I would suggest looking at college sites and seeing their views on gap years/deferred entry. I think Christ's are happy to accept deferred entry, but am not 100% sure on that one. As your course is PBS, I don't see why the majority of colleges would look down on your application, but I think that some colleges would like a reason why you're deferring (eg. travel, work/work experience, health). If you have a particular college in mind already, email their admissions office directly about how they feel about deferred entry and don't forget to mention your course.
Hope this helps in some way, I don't know all, but this is what I do know.