I believe this is a Davidson item, known as M.T.1 posy set (the mould for which probably came from Matthew Turnbull). This info comes from Chris & Val Stewart and you can see the item on their Davidson website (Identifying Davidson Glass Post WW2).
The item interests me as it is known in Carnival Glass. I believe it was almost certainly made in Carnival by Turnbull. In Carnival it is known as the 'Towers' vase, and is widely (and incorrectly) (mis)identified as Sowerby.