Hi,
Welcome to the Forum.
I don't recall seeing that set of marks before, and can only supply a guess. I suspect that your ladle was retailed through A.B. Savory & Sons, and perhaps made in Birmingham by John Gilbert, see:
http://www.925-1000.com/silverplate__OSP2.htmlAlthough Savory's did have their own manufactory in London, they were also important retailers and doubtlessly would have bought in from outside when the price was right. Savory's were known to retail Gilbert's products.
The 'PGS' stands for Plated German Silver, a popular name that was used up until WWI, when, as retailing term, it fell out of fashion for obvious reasons.
Trev.