An area containing some real rarities - see the excellent book by Theo Brauwers 'SCARCE VICTORIAN POSTAGE STAMPS OF GREAT BRITAIN ON COVER' - very fine book by a very knowledgable German postal historian living in Belgium !! - which lists the known usages with pedigrees - with many illustrations in colour. Totally recommended and available on the book section of this website. If you want a real challenge try collecting single frankings of these issues .....