Second Year, 2:2 (51%), what should I do? Watch
I'm not sure if you can retake a year just because you're not happy with the grades. I think you can only do it if you actually fail any modules!
I studied in Scotland with an average of a 2:2 for each year apart from my last and successfully graduated with a 2:1. My advice is to carry on. I was in the same position, working hard and felt I wasn't getting the grades I felt I deserved but knowing I couldn't resit or afford to mess up anything made me work harder in my final year. It is definitely doable, you just need to put in that extra (EXTRA) effort!