Inside the Little Plastic Castle

The UK uses 'units of alcohol', search on that and you'll find a bunch of comparisons. The recommended weekly limit is 14, spread over at least three days. A 25ml measure of spirits is 1 unit, for an ABV 40% spirit, while UK beers tend to be 2 to 3 units a pint. Gin is typically 35 to 40% ABV, vermouth 15 to 20%, so ABV for your Martini depends on how strong you're mixing them ;)