Hi Sweetcheat,
No I don't think they have excavated the burials, I was focussing on the buried stone between the two cromlechs the water board had found ... but if you read the following link, you will see that there was also a 'dressed' holed granite stone in Tintagel churchyard, and that some of the early burials were covered by barrows very similar to a bronze age tradition though they were presumably christian or maybe not....

http://tinyurl.com/ykunrzd