We had some painting done on our wooden window frames, soffits,
fascias and cladding
about a year ago and the paint is already cracking in places (and
peeling in one place).

Some of the wood was a bit manky beforehand and the men replaced some
wood
and filled it in other places.

At the time I noticed that the paint used wasn't a quality brand that
I recognise like Crown
or Dulux (it was just labelled something like 'White Gloss Paint') nor
did the filler they used
specify 'for exterior use' or anything similar on the tubs.

Also I saw no sign of any tins of wood restorer/preservative/hardener
being used on
the decayed wood before it was filled and painted

The painter now claims that the cracking is due to water ingress from
leaks at the edge
of the roof. This is plausible in one place where the paint has peeled
(rather than cracked)
off the soffit, but there are other places (such as window sills
(exterior window sills- not
sure if 'sill' is the right term) where there isn't anywhere for water
to get in other than
via the paint cracking.

Rambling a bit here, so I guess my key questions are
i) how rubbish was the paint and filler used
ii) Should they definately have used some kind of wood restorer/
preservative/hardener
on the manky bits before filling and painting - do such products
work.well?