Outer fuel temperatures much cooler than inner is normal on A319/320. When in the descent, the outer usually warms up possibly due to spill-back from the IDG cooling circuit.
There are two CBs on VU49 overhead for the FUEL TXFER VALVES. Pull them and, BINGO, the valves open and the outer fuel transfers. We used to do it in the company I worked for when I first converted to the A320 (11 years ago) because some old lags didn't trust the auto system! It's not an approved technique of course but the knowledge just might get someone out of a sticky situation sometime.