To answer your questions,
@M.N.D and
@CrunchSlaughtered
That sounds like an addition more than a replacement, so is it going to be more of your in-town personal car, if you don't mind me asking?
Yes, an addition. Originally I was going to get it to replace the 318i, but I've only had that 15 months and there's no point changing it so soon. At the moment the 318i is my "go to work" car and general in-town car, BUT with the ability to travel 2,000km in comfort over a weekend (if I don't want to go back in the X5). I do use it to drive from Holland to the UK (will be doing that this Friday). The thing is, my commute to work is 3km. So when I started looking at the 330e more, that was actually perfect for what I need. 95% of my driving in my 318i is within 30km, and the real world electric range on the 330e is around 45-50km. PLUS, it has the petrol engine for those long journeys to the UK and back. Ideally I would just get rid of the 318i and get the 330e, but I would lose too much on the 318i, so I'm just going to hold on to it.
I could order a 330e sedan now and get it in April, but I think I'm going to wait until the 330e Touring is available to order. The sedan has a particularly small boot due to the fuel tank taking up space, and with a baby you need all the room you can get. Also, I believe BMW will launch a 320e at the same time, so I'd like to look at that too and decide whether it has enough power for my needs.
So, my future plans are:
BMW 318i = Mainly for around town with occassional long distance work, particularly if I need to park in areas I don't feel comfortable parking my X5. It's 15 months old. I'll keep this until October 2021.
BMW X5 = Mainly long distance work back to the UK, as long as I have somewhere relatively safe to park it. Also for local journeys when family are visiting and I need to fit two adults and a baby seat in the back. I have no plans to sell the X5. It's 6 months old. I have no plans to sell this.
R8 V10 = Fun. It's 8 years old. I have no plans to sell this.
BMW 330e Touring = Commuting to work and anywhere within 30km, combined with occassional trips to the airport to pick family up and the UK. Not ordered yet.
Speaking of the G2X 3er, I have to say that I like it a lot, but for me there's no 3 series that I didn't like, and while I prefer the traditional 3 box layout of the saloon, the Touring is the more practical choice, and the G21 looks the part.
Choosing the 330e is the best compromise if you find the electric-only range sufficient for you daily commute, while having the petrol engine to kick in whenever the battery is low.
All the best

Have you decided which spec and colour you're going with?
Oh yes. It's very clear in my mind, thanks to seeing a 330i Touring at the dealer last week. I didn't see my "exact" spec but the exterior colour is the same.
Oxide Grey
Black shadowline, including front grill
19" 791 M wheels in jet black
Did you consider a hybrid version when you were choosing your X5?
No. The X5 45e wasn't available six months ago, and my X5 is used mainly on long distance journeys, in which case diesel is better suited to that.