Winter in the UK

Apparently they tell you to bring the succulents indoors when it starts to get cold in the UK.

It’s better to leave succulents and pelargoniums out as late in the season as possible, but once frost is forecast in your area, get them indoors or under glass.

That’s good advice if you care to take it in the UK.

My advice if you live in the UK is to wear a scarf. Wool, preferably. I prefer stripes myself. Striped scarfs in the UK are a good idea.

I wonder what it means to put your succulents under glass in the UK?