Time travel and aliens

[jenga]

Hi,

I'm looking for 2 books that I read in the late 90's, or maybe 2000/01. I think they're both by the same author, but am not completely sure! I'd really appreciate your help in finding them.

The first one is set in England I think. It starts off with a group of people who are on holiday .. with a tour guide, who visit ruins of something. I think it was a Roman amphitheatre. Somehow, they time travel into the past... it happens again and again, and the story follows what they do in each time period. The only thing I really remember is that some people 'land', after time travelling, in the same place as another object. Like a stone that in there original time has moved, but in the past is positioned exactly where they appear. Another example was someone 'landed' in the same place as a bee. Some of these people died, but some of them exist as part rock, part person. They went off into the woods and lived apart from the non-affected people. There was also a village/town nearby but I don't remember how that fitted into the plot.

The second one is focused on a man. He starts seeing aliens. Other people do too. I don't remember the plot - only the ending. You find out that actually, there are no aliens. It's some sort of mass hallucination... I think it had something to do with changing magnetic fields caused by magma causing these hallucinations.


Thanks!

Jenga