I've only ever seen pork pies served cold. Well, room temperature. Usually in the manner @Anna Ndescribes. I guess they were invented to be eaten that way - perhaps in the fields after a long morning's farmwork. I had one last summer as part of a ploughman's lunch in the UK when I visited.
Cornish pasties are normally eaten at room temperature and were also designed to be eaten at work in Cornwall's tin mines.
Sort of bag lunches with edible bags. Pork pies are also a staple of picnics.
Note exception: Yorkshire pork pies are eaten hot.