What's the difference between UMS my raw?

The raw mark is the mark you got from the actual paper - for example a lot of the science papers are out of 60, so 48/60 would be a raw mark.
UMS are scaled marks, depending on what percentage of the A-level is made up from that paper - common values are 90/300, 105/300 or 120/300.

It is often said that for an 'A' you need 80%, although that isn't true - grade boundaries are set based on the raw marks, and then the 'A' grade boundary is awarded 80% UMS (so if you have 80% UMS, you could have in reality achieved only 70% of the marks if the paper was deemed to be hard).

As for your question, yes, it is definitely possible for you to achieve A's. You achieved two high B's in your January modules, which means that you only need to achieve a few marks above an A from your other two exams to balance it out as an A. It is impossible to say what raw marks you'll need, because we don't know how easy or hard the papers will be, but you'll need UMS scores of 159/210 and 163/210 (if my numbers are right) from your two subjects to achieve A's in both.