Thanks Ray, I love those glasses - we use them for our (home-made) liqueurs! There's no marks on them at all, but the box they came in was marked Astra Glass. It was one of those boxes with slots the shape of the glasses so it appears it was the right box (sadly the box was lost some time ago). We'd sort of dated them to the 1950's (my Mum and Ivo both thought this) but I've not been able to identify who Astra Glass were as yet.
Added after an eBay search: there was a box of Astra glasses listed under no. 7303705123 in the same design box as mine were.