Thank you all for your comments

Keith, I think Hercules is a real possibility - but I'm struggling to work out who the other characters are and how they fit.
The only drawing or painting I've been able to find that includes some of the characters is this one which has a young lad and horses and an old man - no sign of Hercules though. However I know absolutely nothing about Greek Mythology so haven't the faintest idea how those characters might fit together, or whether they are 'independent' depictions rather than telling a story. I will do some more searching though.
http://www.metmuseum.org/Collections/search-the-collections/90034217?rpp=40&pg=1&rndkey=20130617&ft=*&what=Graphite&who=John+Flaxman&pos=26
Ivo, I made the fatal error of using the wrong phrase without being able to support it

I don't know why 'I'm pretty sure it isn't French'. I should have said, 'despite the opaline looking French to me in it's make up, my instinct says it isn't French, based on the shape of the cup, the fat knop at the stem and the design of the painted enamel, and the way the enamel is done. But that's just instinct and I could be wrong.'
Despite what the pics might look like colour wise, it's quite a 'fluorescent' azure blue and I've not actually managed to find any blue opaline glass that looks this colour yet.
I'd love it if it was French

Paul,
'You don't comment on the surface texture - from what little I know about opaline - and especially remembering back to the very long discussion we had some time last year, isn't the surface of opaline supposed to be smooth - whereas this appears almost sand blasted.
You don't mention the sunset glow, so assume this doesn't have same - in which case might this simply be translucent blue glass- rather than opaline??'this vase is opaline glass. For reference - please see the thread where this was discussed at length and in particular on page 11 of that thread a link to Roland Dufrenne's site
http://www.glassmessages.com/index.php/topic,51033.msg290574.html#msg290574 as well as the link to La Cristallerie de Clichy, which shows a large number of opaline piece over a period of time, and demonstrates the development from opaline glass with an opalescence (an example being bulle de savon) to opaline glass that does not show that opalescence.
Opaline glass often has an exterior satin glass surface. Sometimes opaline glass with a satin surface is enamelled and sometimes it isn't. I've posted pics here of a blue perfume which also dates to c mid 1800's (will try and find better pics to demonstrate the opaline of the glass base later)
'Assuming this to date from the 3rd/4th quarter of the C19, can you see the sort of base wear that you'd expect to find??'I don't assume it dates from the 3rd/4th quarter. Do you have a reference for it being this late in the 19th please?
I believe it dates to c.1850 possibly a bit before or a little later into the 50's - for reference see CH British Glass 1800-1914 page 141 where it says 'After 1851 many of those styles either waned in popularity or disappeared completely' and page 136 which references an Etruscan white opaline vase from Richardson with the similar shape cupped rim etc. Also page 139 where it references Davis Greathead and Green's vast array of colours of 'Egyptian, ETruscan and Grecian styles' glass on display at the 1851 exh.
I notice that Gulliver and Hajdamach discuss the pix/images on generically similar pieces as being 'transfer decorated' - what makes you so certain that this one has been hand painted - can you detect brush strokes, for example?? To my eyes the pictures looks exceptionally uniform in shade of colour - not perhaps the slightly varying shades that might come from painting.See page 139 where the Davis Greathead and Green vases are discussed and are hand enamelled.
I believe this vase is enamelled. I've attached pictures of a transfer printed vase I have and also close ups of the damage to the decoration on this vase. Perhaps I am wrong? does this look like transfer printed decoration? The one that is transfer printed is completely flat on the glass, you cannot feel anything and you can see where the transfer has slipped on her arm and also on the urn.
On this blue vase the decoration is slightly raised from the surface and you can feel it. Also where there is damage you can see the enamel has flaked and where there is crazing to the enamel surface particularly on the greek key design on the foot for example. My photo isn't very good but it's the closest blow up I can do to show you.
With regards to where it was produced, the shape looks most like a Richardson vase to me but only at the top and the body. The foot and stem do not. The foot and stem look most Bohemian like to me, but the cup not necessarily so. The hollow foot applied to the body in the way it has been reminds me of another of my opaline Bohemian vases and makes me think Bohemian. The purity and elegance of the actual opaline looks French to me but could also be Bohemian or could be English given the plethora of colours apparently exhibited by Davis Greathead and Green. The whole presentation of the vase, the off white on the bright deep blue makes me think it was made to 'replicate' a Wedgwood vase of perhaps an earlier era, which makes me think English. But the decoration looks Russian.
The only thing that looks French on the vase at all to my eye, is the purity of the opaline glass but I've not found a blue to match.
But I could be wrong

m