When I found this, not knowing a lot about UK glass, I thought it was of Monart heritage.
Now suspect not from that manufacturer now due to the shape and the fact it has a 'ring' to it. Not a dull sound described in what I've read.
Base is not ground.
Applied pontil button has pontil scar and below base height some 3mm.
Inside of bowl has convex profile when distorted by application of button.
Colours reasonably close to actual in photos attached. Flash used.
If not Monart then who, and what possible age to this piece, please.
Sizes:
Height: 100mm
Diameter: 140mm OD
Wall at rim: 4.3mm
Pontil 'button diameter: 37.5mm