UK - health visitors

I’m a first time mum to a 3 month old little boy. My heal visitor has gone on maternity leave so I don’t know who my new health visitor is, no ones been in touch and I don’t know how often they come out to see you and baby?

I’ve seen posts here and I’m guessing they’re from America about seeing people about when to start feeding baby and getting the ok about it.

He’ll be 4 months in the 16th July and I’m just wondering about giving him a bit of baby porridge? Do I need to wait for the health visitor to say it’s ok or should I just try it with him when he’s 4 months?