If you join july 15 intake
you will be having AS exam in june 2016, result will be released in august.
thus, you will have to apply UK uni by using your forecast result or AS result.
You will meet internal deadline (college's deadline, they need time blah blah blah for application ) in oct or nov, it depends on school.
However, the external deadline (Uni itself) is in jan,
Don't forget that you will need to write a personal statement, it burns time too.
If you get accepted by (UK) uni, your course will commence in sept.
ps you will sit for A2 exam in oct16, result will be released in jan17.
by that time you will need to update your result for the sake of application, or maybe scholarship.