There is a compact and a quiet Liz dual-boiler available here for sale priced at £900 with warranty here ! This will save you some cash to get a Niche priced at £500.
You said 5 people want latte. Assuming, they are going to be back to back shots, @MediumRoastSteam, who has one, can advise if it will serve your purpose. I can’t judge as I haven’t used that machine.
The ACS minima is a very good machine and will serve you very well. It is a bit noisier than Liz, packs with tons of features, you can add a paddle later and I think it will cost you about £1400 direct from ACS; and, they will advise you the actual cost to you before VAT and duties. If you are going to write to ACS, please ask them the cost of ACS Vesuvius. It might not be significantly different from Bianca.
If you are happy to stretch another £400, Bianca would be a great choice.
These costs do not include the costs of a grinder or water.
Edit :
I won’t put bottled water on a new machine, as I won’t feel comfortable. The mineralised (bicarb) Zero Water would be the bare minimum for me.