This is a very big question because there are many aspects of what Britain was like and there were different conditions in different areas of Britain.
In general, one can say that Britain had an Iron Age civilization that was pre-literate but which was also becoming more organized and more peaceful. By the time the Romans got to Britain, the famous hill forts of the Iron Age were no longer used as much for defense and there were towns that were completely undefended. This shows that the society was, at least in some places, coming to rely more on trade and less on warfare. Because this was occurring, there was also more of a market for metalwork and other goods that could be traded.
This is not to say that Britain was completely peaceful. However, the Britain to which the Romans came was becoming much more of a civilization of towns and trade rather than one of hill forts and war.