if your the kind of person who thinks it's okay to apply for sixth form this late then yes, you probably will struggle. As for english lit and sociology they're both around the same workload but english is more respected. though you might have an easier time with sociology because of it's slightly technical nature which i assume must appeal to you more because your taking history and economics.
p.s just read you wanna do law at uni. in that case take out psychology and have maths. and i'd say you have an awesome set right there. also keep english lit and DO NOT change this into english lang (it's not all that bad but english lit will serve you better).