Hard wired ceiling smoke alarm chirping

[LOVELYDOVEY05]

I guess the battery needs replacing but instructions indicate mains electric needs to be turned off before doing this. Would I be better to get an electrician?

No, it’s simple enough, takes a minute. Just turn off the electrics at the fuse board. Have the new battery ready to hand, check the instructions for which type of battery (if you still have them) or pop open the alarm and look.
If you’re still not sure though then just get an electrician in or a handyman.

You can just flip the fuse switch. Is it definitely a battery that can be changed? Mine were doing this recently and I discovered they had ten year rechargables built in, but now the entire unit needed replacing. However, they just slid off a base plate that was attached to the ceiling and a new one slid on. Did it myself after they progressed from occasional 'cheeping' to full on 'repeated blaring at 2am, 4am, 4.30am' etc. When I looked more closely they actually had an expiry date printed on them which had gone several years over!

Is if def battery or could it be the sensors (has it gone off unexpectedly lately?

If so - hoover it (all the vents and bits). Mines does that every few years and last time I did it (at about 4am, naturally!) a spider crawled out and evicted himself.

It is about 7 years old I think. We have some new batteries so will try.
The alarm has been going off due to a new oven being put in but when I use the extractor it seems to stop it going off. Annoying but so is the chirping sound

If you've got the manufacturer's instructions, it should be easy. Have you?

Don't assume it will be the same as somebody else with a different model. Some do not have replaceable standby batteries.

They may also chirp if the hardwired electric circuit has failed.

p.s.

for kitchens, a "rate of rise" temperature sensor is preferred to a smoke sensor. It will tend not to go off if you burn the toast.