These web pages hopefully provide some information that may help your stay at the flat.
Utility cut-offs
Gas - the main cut-off valve is the red lever left of the gas meter, in the upper cupboard by the kitchen window.
Electricity - the main switch is in the consumer unit, in the lower cupboard by the kitchen window - lift the metal cover - the big red lever on the right.
Water - the main stop-cock is at the back of the cupboard under the oven by the water meter - clockwise is off.
Replacements bulbs, batteries, hoover bags - read here
Maintenance, cleaning materials and hints - read here
Detectors
Checking the smoke and carbon monoxide alarms is easy and definitely worth-while!
smoke/heat detectors - although these have batteries as a backup, they are mains-powered normally so their batteries rarely need replacing. Each has a 'test' push button, and as they are interconnected, they should all beep when just one button is pushed.
carbon monoxide alarm - these can start to beep and show 'lb' when the battery is low or if nearing the end of their life.