According to Philip Eden's website, the provisional figures for March
a

CET 6.3°C (-0.1 degC)

England Wales Rain: 65.9mm (90 per cent)

E&W Sun: 135.9hr (120 per cent)

So, for the areas specified, the cold first half of the month and the
mainly mild second half just about cancelled out, but the dryness and
sunshine of the first half more than compensated for the wet and gloom
of the second half. (Obviously particular regions may have had different
experiences from that.)
--
John Hall
"Acting is merely the art of keeping a large group of people
from coughing."
Sir Ralph Richardson (1902-83)