Can I ask what data packages yoi have on mobile phone ?

[Rosierambles]

I'm in between a rock and a hard place trying to sort a new contract but currently have three lines with one provider and I can share my generous data package with them and pay low ish contract cost for them (sim only for DS2 and a handset contract for DS1 which compared to other providers seems a lot but has a year left )
None of us have new phones but I think we all use a fair bit of data but here's the thing- my iPhone only had the data used since I got it so I don't know what I need per month and the same for boys.
I've got a great Tesco offer and have asked for my PAC code to leave but don't know what data package to get and also if I'll now need to boost their mobiles with extra data undoing the cost of the saving on my new contract
Current provider wants £67 for an iPhone 15 unless I switch to their broadband and they knock £20 off.
Painful. It's like buying a car these days !!!

I’m on Three. Have been for about 15 years now.

Best deal is with ID mobile but I'm dithering as I'm not sure if they'll be good for a family deal when I bring DS on board.
Why is this so hard for me ? I'm finding it so stressful when really, how bad can it be??

ID run on Three. I find it slower at times in surprising big places, but other than that it's great.
The app to use ID is good.
I brought my son's mobiles in my name and when they turned 18 I simply got them to take a new contract and port existing number over. Before that the contract was my name, my email address and they didn't have the password.