Thanks Keith but it is definitely not Lowestoft porcelain, I know it too well (I lived in Lowestoft for 13 years, just recently moved from there), and have a small collection of Lowestoft tea bowls and saucers, jugs etc Lowestoft do not mark with pattern numbers, but some items may be marked with one number in blue, for the artist or a blue crescent mark.
I used to go to Russell Sprakes Lowestoft Porcelain auctions regularly, up until he died in Aug 2014. Someone else is now running those auctions at different venue for the last year.
It is probably by Keeling / Factory X, just had me stumped, as searching through books, V&A collections online, general googling, I couldn't find another for a definitive ID.