If you're aiming for 'good' universities in the North West (e.g. Manchester), you will typically require a third A-Level to study something like law. Still, there are some options available to you.
1. Consider sitting a third A-Level
Although time-consuming and potentially costly, simply having a third A-Level will definitely open more doors for programmes like law. This is especially so if, as you suggest, you plan on attending higher-ranked universities.
2. Consider universities that use UCAS tariff points
While it may not be at the university you want, it may be the quickest way to streamline a course in law. Depending on the university, the accumulation of your UCAS points might make you a strong applicant.
3. Consider an Access to Law course
These typically take around one year and will make you a more competitive applicant - though nothing is guaranteed.