I need some guidance. Yesterday I went to Coldrum and on arrival found someone sitting cross-legged eyes closed, headphones on, right next to the stones, his trail bike lying on the ground equally close. Like many of us I wanted not just to appreciate the beauty of the site and its setting etc, I also wanted to take some pictures but not ones that included this person and his bike. Okay, I thought, give him some space and time, don't be impatient, but after about 20 minutes he hadn't budged and clouds were gathering threatening to shut out the sun altogether. Should I gently suggest he might consider moving out of shot? Would it be seriously uncool of me to interrupt his meditation? Whenever I visit a circle and there are others there wanting to take pictures I'm always careful to stay out of the way and wait my turn. In the end I managed to take pictures from oblique angles omitting his presence without disturbing him but I left feeling slightly irritated and wondering if I was being selfish. What do others feel?

After waiting half hour I would have nicked his bike and come back later ;)

Ironstone, I think you need to fight your Britishness!
Seriously, I have a thing about this sort of thing. The places are owned by everyone so the only civilised thing is to share them timewise (and leave them pristine of course).
Nicking his bike is rather a nice way of making the point. They are "our" stones and "our" bike....

Just be nice, none of us own anything in the long run;)

Something similar happened to me when I visited Boscawen Un a few years back - we sat outside the circle and waited for the two women to go, which they did eventually. Fortunately it was a beautiful warm afternoon so there was no rush. We had the circle to ourselves for about 15 minutes before other people turned up. I don't think I would be brave enough to ask someone to move as stone circles are often in remote places and I'm a woman, albeit usually with someone.
There are other sites where it is a given that people will be in the way - Castlerigg springs to mind, and of course Stonehenge.

Guess it depends upon how you approach a visit to a site; whether you see it as something 'nice' to look around for a few minutes and take a few pictures, place a tick in the box .... a hobby.... or something that has the potential to profoundly move you. Whether that be on an aesthetic level - the shape, dimension, grain, texture of the stones - or in relation to where the monument is located, the backdrop, the way your attention is drawn to other points of the landscape... the sound of water, perhaps?
I'm very much the latter and like to spend all the time I have available on site, usually several hours or more, watching the changing light, moving shadows (on the rare sunny days) and cloudscapes. I think it may well be that I'm slow on the uptake and need a while for things to sink in, whilst others can appreciate scenarios in a limited time. Guess you are what you are. I have no problem with other visitors as long as they are quiet and respectful to the surroundings. If they aren't, that is a different story. There have been a number of incidents, much less so now since I try to visit popular sites early morning or dusk.
In my opinion prehistoric sites are for everyone showing respect for others, and I would be gladdened to see a man or woman so into the vibe as to be sitting in silence taking it all in. Much better than barely interested tourists. Mind you it is an extremely rare occurrence in my experience. I usually make it clear that I'm here for the duration but happy to move for a while to allow clear camera angles.
It's the bongos I can't bear! Seriously, we walked up the hill at the end of West Kennet Avenue today to watch glorious Silbury come in to view; passing a fine chap who was fiddling with what I thought was a Hawthorn tree but was informed was a Blackthorn tree. I asked what he was doing, only then noticing various ribbons; corn dollies; wicker hearts and even a fizzy drink can on the ground at his feet. I'm very new to the lure of these places (as I'm sure you can all tell), and hadn't seen a bedecked tree before. He told me that some of the ties around the tree could kill it and stunt it's growth, and that the materials used should be loosely looped around the branches so as to blow away easily, and that they should be biodegradable.
The feeling I get from Avebury, West Kennet & Silbury is peace, awe and being grounded in a place; like it's the right place to be; like it feeds something inside me! Oh dear I'm not very eloquent. Anyway I'm a newbie & I'm looking forward to experiencing more special places. We tried to visit Waylon Smithy the other day but the car exploded! Will try again tomorrow.