The only thing that's a ONE HUNDRED PERCENT CERTAINTY is that the folks would HATE anything that DID resemble the primitive music of that time. I'd suggest you follow Hollywood's example and go for lutes, trumpet fanfares, gorgeous dark-haired actresses with finger cymbals (for that exotic 600 years before Saladin, Arab feel)

Oops, and don't forget all the Roman names (remember Britain was 'occupied' for a long time)

Cheers

Rick