Thanks Mike, that is very helpful.
To briefly address those
1.6.7
Are in the same ballpark and require a proper understanding of why items were registered. Few were "I've thought of this neat design". The majority were copying / following trends / innovations allowing new shapes to be made. On the design to product, there is little info from the Victorian era. The best resource for that one is poster James Measell who knows more about mould production than anyone here, he has posted some useful stuff on facebook about moulds. I have consulted with James on a few things.
2.
Colour ranges tend to be narrow unless an item was hugely popular, like the Derbyshire lion or the Burtles Tate swan, both of which are in the region of 15 colours. Full colour ranges per item will never be known with certainty as there may be few or no survivals of rare colours. You may note from a few of my recent posts that I have viewed the spoil from the PV archaeological dig, this showed some colours which were otherwise unknown from their regular production, I will be covering that.
3.
There are some reports of work inside a Victorian glass factory in Manchester and Warrington, though PV was not one of those covered. They tend to be concerned with government reports into child labour.
4.
It is known that Molineaux Webb purchased the PV moulds after the factory shut.
5.
There are few surviving adverts and 80% of them cover known registrations. I do have permission to show some catalogue images which will more than suffice. I've actually collected more unregistered pieces than registered. I showed a rather routine one in a post a while back, of an 1880s unregistered butter dish. If there is a concern on coverage, it is that about 40% of registered designs have no surviving examples. Some of these will never show, such as railway carriage lamps, or liquor barrels for pubs. It is a dilemma whether to show the original design registrations in a book, as many have been covered by Jenny Thompson and it is possible to post any of them on here with a copyright watermark. All registrations will be catalogued though, with rarity estimation and colour range where known.