Mains smoke/heat alarms

Advice please.....just installing mains smoke alarms with battery backup 4 of them linked together.....very nice if a little unsightly.

1. Should they be on their own circuit in the Consumer Unit - assume non RCD side as they aren't earthed?

1.5 What size breaker.....6 amp?

2. Do they need an FCU to isolate them?

3. Thanks for other answers on other stuff so far......

Yes if you have got room

They should not be on the RCD side because you want to minimise the chance of then losing power. In the event of a fire the RCD will trip fairly soon as wires or appliances get burned and you will probably have forgotten to renew the batteries.

Yes

If they are on a 6A MCB what will the fuse in an FCU add? Nothing. You can put a DP switch on the supply as an isolator for servicing if you like, if the CU is relatively inaccessible.

Thanks...an isolating switch would be in the same easily accesible cupboard as the CU, so if it's not essential for regs I won't bother?