I have just had a gas fire removed from what was originally used as an open fire. I want to know if I need a chimney liner and how do I know if there is one already there? We would like to burn logs and coal.

My best advice to you is to have your chimney checked by a professional for the use you desire. Burning coal or wood can be very dangerous in a chimney not designed for it and especially if it has not been used for that type of fuel. Safety is always better than sorry and there is more to burning solid fuel than just a liner. You were smart to ask that question instead of just using it.