Mention for a little typo, you probably mean BA in PPE at Oxford.
Your profile seems solid for master's in econ. Being top 5% of the class from Oxford is a very good signal. Your law degree is still worth mention in application as you get a distinction. One thing I would add is for you to attend school where there is well-known professors in your field of interest and could be your supervisor. These programs usually requires you writing thesis thus field of interest and supervisor are important. Also, you will have good letter of recommendation writers. IMO I would suggest you enroll master's in UK as most of them are very strong. Also, as you are UK citizen, you have more chance of getting some kind of funding, or loan. Look into each school in your radar to find if there is anyone like I said. If you get a distinction again from, says, Oxbridge you should have decent chance for top 10 programs, or top 30 for extreme case.
I can't say anything about UBC and BGSE but I think Oxbridge would sounds better.