1.
In house policing degrees are not of a very high standard. They just aren't. The academic level of them is mediocre at the absolute best. The scope of a policing degree in terms of law is very limited indeed and won't even cover what is taught in an LLB criminal law module.
2.
3-4 years as a police officer (which is the minimum you'd have to serve to come out with a degree) isn't going to give you very strong experience or make you a particularly attractive candidate. Most of that time will probably be spent trying to make nonsense domestic violence cases go away or sitting and watching people with serious mental health issues urinate on themselves in custody. You would have to have a strong plan and be willing to see it through - that would mean either at some point going down the detective route and getting strong case building experience - or getting into a police criminal justice unit and stay there for at least 5 years gaining experience - an absolute minimum of 8 years in total from joining.