A btech is a lot of work it's not equivalent to just one alevel usually 2. I would drop it because you are really out doing yourself with all the work. If you are interested in criminology as a degree you would usually need a psychology a level. On the other hand for example if you decided to pick history as a degree some universities allow you to mix it so it would be history with criminology but to find out you'd need to look into university brochures and see what's on offer.