I feel much the same as you do, Wideford. Pre-history and history merge seamlessly at different times in different places and the artificial divisions that we use (Neolithic, Bronze Age, Iron Age etc) had no meaning to the people living at the time. No one woke up one morning and said "It's the first day of the Bronze Age today so I don't want to see anyone making any more flint stuff!" (some very fine flint work continued well into the Bronze Age) I feel much the same about national boundaries - the further back in time you go, the less sense there is in worrying about present day geographical boundaries. I have always believed that you can't really begin to understand British pre-history without considering European pre-history.
When contributing to someone else's website, I try to follow the ground rules. Rude and futile not to, but that doesn't mean that free opinions cannot be expressed and policy hopefully influenced. At present TMA's cut-off point is the Claudian Invasion and I am sad about that, but accept it of course. I hate the Romans, but the population remained almost entirely British and the ordinary people lived out their lives with additional burdens. Very few had villas, mosaics and under floor heating! Stopping at 43AD means that British (I don't use the word "Celtic") settlements, burials, agriculture etc which went on despite the occupation are not recognised. It is a bit like saying that Indian culture ceased to exist during the British Raj. Personally, I would love just the sort of website you describe with a cut-off point of the Norman invasion (it has to stop sometime) This has no logic other than it would encompass my personal interests. It isn't going to happen of course and it is unfortunate that "Dark Age" websites are mostly concerned with re-enactment. Like many of us, I use the Portal as well and have no patience with the squabbles. One of the reasons that I visit the Portal is that they do include Dark Age Pictish stones and Pre Norman crosses (both are two of my passions) The other reason is that it has some international coverage.
I've gone on a bit longer than I intended so I will shut up and await any Romaphobic or anti-Portal response.