yeah thats because i took it off for cleaning.....

The size should be stamped somewhere on the post. Some brands have them stamped on the back, at the top of the tube section but most are stamped on the front, below the insertion mark. So, you may have to remove and clean the post to see the stamping which will be format 2x.x. Just make sure that the post itself is not too small for the seat tube. If the post is too small, the cinch slot in the set tube will not be parallel along its length, but noticeably pinched at the top.

I think it's English. Probably all 531 and might have had the cable guides added, but there were many Brit builders who didn't follow the latest fashions: mixed things like braze-ons from what we'd think of as "different eras". Nice bike with some very nice mixed-bag components.