Hello Flintov!
I share your name, mainly because I have collected lithics for more than 30 years - I guess we'll have to share it!
I am very interested in your finds, as obsidian is my favourite lithic raw-material. It really is quite magical. At first pass, your finds looks very much like obsidian/pitchstone to me.
Obsidian tools are currently unrecorded in the UK, but there is absolutely no reason why your finds might be the first of a similar, (but distinctly different) material - pitchstone, possibly from sources in Scotland to reach as far South as you mention. This thread has already explored some of the possibilities, perhaps I can add something to the debate. Whatever the outcome, I suggest you record your finds with either your local museum service, or the Portable Antiquities Scheme.
I have enjoyed the priviledge of observing and studying tools of the middle pleistocene/epi-paleolithic/neolithic from numerous sites in the Middle East. In that region, despite sometimes being hundreds of miles from the nearest source, neolithic cultures obviously appreciated the superior knapping qualities of obsidian - it was possibly the very first widely traded commodity aside from foodstuffs. It is widely found on the Arabian peninsular - from the Southernmost sites in Oman and Yemen all the way up the peninsular to the most likely (abundant) sources in the Levant/Turkey.
As far as the UK is concerned, since before 4500 BCE, it appears increasingly likely that real 'international' trade, as we understand it, (albeit on a small scale) between small groups of Britons and their continental neighbours was underway. Despite the presence of trade (in obsidian) between our close European neighbours during the fledgling neolithic, I have often pondered the possible reasons why tools of this material might be absent from the UK archaeological record. I suspect the paucity of evidence for the trade in volcanic glass is based on some quite complex factors. At the end of the day, it was possibly just too 'expensive' to trade in obsidian when the Southern UK population of Britain had access to sufficient quantities of high-quality flint to negate a real demand for the product.
Domestic trade in Scottish pitchstone is potentially quite different.
Obsidian and pitchstone are very closely related geologically. Both are comprised of exactly the same constituent materials as granite, but since they have been cooled far more rapidly (particularly obsidian), their minute crystalline structure (similar to glass) exhibits a fine conchoidal fracture. It is possible to find obsidian (at source) of several different types (from the same volcano and the same eruption), such as the obsidians from Green Mountain, Ascension Island, which I have studied at length. These exhibit distinctly differing crystalline structures - and potentially differing knapping qualities. In the case of Ascension Island, the primary source lies in the foothills of Green Mountain. The volcanic glass can be found in 2 distinct areas (albeit very close to one another). One area contains weathered scree (and vast underlying deposits) of very glassine, black obsidian (similar to Glass Buttes, Oregon), while a few hundred metres away, a far more coarse-grained and distinctly 'greener' variety can be found. Both can be readily knapped, but the 'green' variety obviously cooled more slowly than the black variety - its coarser grain can be discerned with the naked eye. Despite that, this coarse grained variety makes savagely sharp tools. A good friend of mine, Will Lord (Son of John Lord) has recently demonstrated trepanning of bone for a TV production concerning Peruvian mummies. He used 'green' obsidian provided by myself from Ascension.
Green Mountain on Ascension has (in geological terms) a fairly recent and active history. The volcanic history of Scotland is more ancient - and this is important when we consider the relationship of obsidian/pitchstone. Obsidian eventually becomes pitchstone; over time, the minute silica crystals grow.....and slowly but surely, obsidian becomes pitchstone and pitchstone eventually loses its conchoidal fracture and becomes utterly useless for the manufacture of lithic tools - inclusions grow and the very nature of the fracture of the material becomes unpredictable - and in lithic tool manufacture, predictability is everything.
Your finds are potentially quite important. Since obsidian and pitchstone have quite unique microscopic 'signatures', it should be possible to trace their source. As such, I urge you to record your finds as widely as possible. Archaeological research is often underfunded, resulting in very, very slow results, but if you wish, I can record your finds on the UKDFD database and will do my best to 'fast-track' some results - I know some quite influential archaeologists. I use a metal detector in my leisure time, but I have a healthy respect for Nigel Swift in regards of his efforts - my first love was/is for lithics.
Best wishes and good luck.
Jon Adkin.