Best deal to add a child SIM with non-smart phone

Hi, I have a Nokia 110 4G for a child and want to get a SIM - don't really need data and want monthly but no commitment. There used to be a £4.50 deal - what is currently the best deal (I can only find £6 ...possibly discounted to £5.40 on a group plan) ? Second question: A friend has a second SIM on their account on the £4.50 deal - can he add another person on at that rate or do new, higher rates apply?

Thanks