Howdy
I don't know the "laws" or regulations in the UK but here in the USA, what you did is illegal. That being put aside, pheasants should not be raised with other poultry, especially chickens. Chickens carry diseases that they can tolerate but will kill a pheasant and other gameirds.
They require a larger area for their enclosure than chickens or other poultry. (appox. 25sq.ft./bird)
The chicks should be fed a complete high protein feed of 24% or better and a clean source of water.
They should have a heat source that provides enough warmth for them until they are fully feathered and can regulate their own body temperature. The brooder should be set up to provide 98°F to 95°F temp for the first week and then lower the temp 5° F each week, until they are fully feathered. Here, in the US, the
Brinsea Ecoglow reviews have suggested that it doesn't provide enough heat for the chicks.
Pine or Aspen shavings are ok to use for bedding, however, do not use cedar shavings as it "off gases" volatiles that can kill birds.
BIOSECURITY is most important when raising pheasants. Cross contamination is the #1 cause of disease and death when raising pheasants and other gamebirds.
Wish you the best with your chicks. HTH