Otis, Raymond Slack's "English Pressed Glass 1830-1900" (ISDBN 0712618716) is currently available via
www.amazon.co.uk from £40 (sounds a lot, but it cost £30 when it was published in 1987!). If you are prepared to wait, you may get a copy via eBay for less (I think the last copy sold for about £25).
Another essential reference book is, of course, Jenny Thompson's " The Identification of English Pressed Glass 1848-1908", self-published in 1989 (ISBN 0951549103). Currently available via Amazon for around £25, but there have been a few recently on ebay for less than £10.
There is also a Supplement to Jenny Thompson's book, published in 1993 (ISBN 0951549111), currently £5.20 on Amazon (and usually about the same the same on eBay when listed).
Sheilagh Murray's "The Peacock and the Lions- The Story of Pressed Glass in the North East of England", Oriel Press, 1982 (ISBN 0853621977) concentrates on the output of the Davidson, Sowerby and Greener glass works but is now looking rather dated (with hardly a reference to registered design numbers). Currently avalable via Amazon from around £12. It does, However have some useful photographs (including a colour photo of the turquoise 'grape and vine' plate as a frontispiece - no mention of date or lozenge, just the lion & star trademark), and, interestingly, a mononchrome photo (plate 65) of the large circular plate with looped edging and floral decoration (shown by Roy in reply #5 of this thread) noted as having a lion and star trademark - so obviously Greener - but, again, no mention of a lozenge or date .