The figures quotes on the dashboard appear to be incorrect. I only have two fillups so far which means that all three quoted figures should show the same MPG.
However, they show the following:
avg (UK MPG) - 59.4;
last (UK MPG) - 59.4;
best (UK MPG) - 49.5;
You found a bug. If you had only one fuel-up with a calculated MPG and in the UK view, the best tank wasn't being converted to UK MPG. It should be working now.