The world of law is incredibly competitive. Far more competitive than, with all due respect, it appears that you seem to appreciate. To become a lawyer or barrister who is in good, stable employment, then you will need to prove yourself worthy, because being a barrister is not an easy job. The issue is simply that there are far too many people getting law degrees and not enough pupillages/training contracts available. As a result, you are going to need to out-compete a fair amount of people and frankly there are just so many people out there who have 2:1/first class degrees from unis that are better than the ones you're applying to.
As a general rule, I would say that you are unlikely to be able to get a good pupillage if you don't have at least a 2:1 from a Russell Group. It is perhaps a bit harsh but you really need to understand how cutthroat the competition is. You don't need to go to Oxbridge, LSE, Durham or UCL in order to find good employment, but realistically, if you want to become a barrister at a decent firm, you will have to aim higher than you currently are.
My recommendation for you is to have a look at the University of Liverpool's law course (or similar RG unis). It is (if I recall correctly) only ABB, which, provided you put in plenty of work, should be within your capabilities. It's not as good as the rest of the RG, granted, but it will probably present you with more opportunities than Westminster.