I,ve just finished re- reading ( my 4th time ) Bernard Cornwell,s Arthurian trilogy .First book The Winter King followed by Enemy of God and then Excalibur, you should be able to pick them up cheap in any second hand bookshop. I,ve always fancied a campaign based on the books. The time period is 480 - 525 a.d. I recommend photo copying the map at the start of each book , I hand coloured mine, it makes it easier to follow the changing alliances and twists and turns of the plot. Good reading.