Earlier quoted context omitted.
I disagree that the UK is metric at all. They try to teach us to think metric in school but in the real world almost everything is still imperial. We hear imperial units every day in this country. We hear it when we discuss body weight, driving distance, cooking, size of most things, etc.
I'm British. I live in the UK. I'm in my thirties. I do a person's height in casual conversation (on forms I write it in metres) and driving distance in Imperial measurements (often; I use kilometres when I'm talking to someone I trust to know what a kilometre is, which is generally anyone under about 40). I do depth and altitude in metres, but sometimes I'll use an old chart that has feet (or sometimes fathoms, but…
Regarding the steak point, do you never ask for the 8oz or 10oz steak?
For curiosity, I'm just outside Glasgow, where are you?
Edit: Gordon Ramsay recipes: http://gordonramsaysrecipes.com/
Butter update: Butter is measured in knobs.