Does the seam go to lip of the crown?
That will help with dating.
Please post pic of crown.
That Pepsi bottle is very different from what we find in the United States. It appears to be what is called a slug plate bottle. Bottle makers would make a mold with a round or oval indentation in it. Then they would have a plate made that is embossed with whatever they wanted to have the bottle imprinted on and inserted into the mold and blow bottles. So the same style bottle could have many different things embossed on it, by just changing the slug plate.
It was done early on but,it was not a common practice for Pepsi or Coca-Cola in the United States. By the early nineteen hundreds they were making bottles and shipping to the local bottlers. Up until the early 70s Coca-Cola and Pepsi was bottled locally. And the bottoms of the bottle would have the bottling location embossed on them.
I remember when I was a little boy watching Coca-Cola being bottled downtown. The whole front of the Coca-Cola Bottling plant was glass, so you could watch it being bottled.
I do not know when Pepsi was introduced to Great Britain. My guess would be in the early part of the 20th century. And your bottle would be one of the earlier ones produced. The reason I say that is because of the slug plate design.
They could have used the slug plate style mold so they could use different alphabets in different countries. So this bottle mold could have simply been used many different countries by simply changing the slug plate.
The marks on the bottom of the bottle are the manufacturers marks, with some research you may be able to find out who made the bottle and when.
Even though I'm a Carolina boy and Pepsi was born in the Carolinas, my soda of choice has always been Coca-Cola, my Mama was from Georgia.
Maybe that's why I was never much interested in Pepsi bottles. And don't have a lot of knowledge of them. So I can't tell you any more than that. But I do believe it is a very early version of a Pepsi bottle for that market.