English question, please help?

Double room has generally facilities for two people with a large bed...a double bed or bigger. If you need to sleep separately, then of course you need to specify that before booking the room for two separate beds. Some rooms have a double bed with a single bed in a corner for kids.

In the UK a double room means a room with a double bed. Double room does not mean 2 linked rooms.
If you want to share a room but not a bed you need to ask for a twin room which will have 2 beds.
A single room has a bed for a single person.
En suite means a bedroom, which may be a double or a single, and a private bathroom.
A suite of rooms comprises, 1, or more, bedrooms, bathroom and lounge.

A "double room" usually contains two rooms with two beds. Sometimes they both have their own bathrooms as well.
You could ask for a "single bed", a small room with a small bed.
You could ask for a "single suite", a bigger room with a much larger bed.
You could ask for a "double suite", meaning two bigger rooms with two bigger beds. Since "double suites" are the more expensive kind, they will usually also have other commodities, like a living room, kitchen, and/or balcony.

If you ask for a double ROOM, you'll get a suite with two rooms. If you ask for a double BED, you'll get one bed that is suitable for two people.

Other possibilites are a single bed and two single beds (in other words, so that two individuals can share a room but not a bed). Unless you specifically ask for a double room, the standard is to get a single room.