HeHe. C'mon fellas, chill
This topic has been around for years.
The conclusion comes to this. The Mesa v30, the Marshall v30 (Actually officially called just Vintage, no 30 tacked on), and the Standard v30 ARE ALL VOICED differently.
Therefor we cannot reliably say they sound different because of where they are made.
Personally I prefer the Mesa v30. I own 6 Chinese v30s, and 4 mesa v30s. To me the mesa's sound better, they are warmer, less fizzy, and the top end is much more pleasant.
Somewhere floating around on the internet is a statement from Mesa. It states if I remember correctly, sometime in the 90's mesa received a new shipment of v30's (all English made still) they noticed they sounded different from the v30's they were getting. They contacted Celestion and said WTF? Celestion said they made some changes (Glue? Paper? IDK) . Mesa said, we don't like them we wan't it the old way. Celestion not wanting to lose a large customer complied with their wishes.
You can buy Mesa v30's direct from Mesa:
https://store.mesaboogie.com/products/s ... dance.html
notice the part where it says "custom made for MESA in Ipswich, England"