This is indeed quite sticky...
Your best option is to email/phone/contact each university you are thinking of applying to and explaining your situation. Then try and get written confirmation of whether or not they will still consider you.
The entry criteria for each university differ quite a lot, for example some say you need to complete a-levels within 2 years whilst others say resits are accepted but only if you achieved a certain set of grades in the first try.
Make sure you do thorough research and contact each uni separately to see if they will accept 4 years of study and if you will be considered less competitive or not.
Best of luck!