No Sue, not Monart.
Ysart Brothers Glass (trading as "Vasart") was set up in 1946. The "Vasart" that RescoCCC refers to above was "Vasart Ltd" (1956 - 1964)
The weight is quite typical of the Ysart Brothers period (1946 - 1956) and may have made by any of the Ysart men at that particular company.