Two things to highlight this month, and one to anticipate.
Comparison with November
Levels in December were generally lower than November. On the November graph the line was above 10μg/m³ for most of the month, whereas for December the line was more often found below it.
November was a rainier month, which I think would tend towards cleaner air. Temperatures were not too different, although December was slightly cooler - average nighttime minimum of 7.4°C versus 8.2°C for November. It seems that colder temperatures tend towards more pollution in Eastbourne, which I presume is due to boilers, and wood burners, being used more to heat homes and offices, etc around the town. However, against these two weather factors trending towards a more polluted December, this month has been windier and perhaps that has swung things by bringing cleaner air in more consistently.
The exception that proved this rule was the elevated level of PM2.5 after Christmas. I commented on this at the time. I have no further light to shed on this phenomenon now, but having looked at other Eastbourne stations on Luftdaten my readings were not unique.
Out with the old, in with the PM2(.5)
As we bring in the new year I expect to see an increased level of PM2.5 due to celebratory firework activity around the town. I would expect lower levels than observed around November 5th, because there will be fewer bonfires, but I am expecting to wake up in the morning and see an uptick on the graph to welcome in 2019. Happy New Year!