Sunsail are one of the biggest companies doing flotilla holidays and bareboat chartering. Neilson are another big company
https://www.sunsail.com/uk/
https://www.neilson.co.uk/sailing
A flotilla holiday is where you all end up at the same place each night but during the day you're free to do what you want. There is also a crewed lead boat that is there to help you with mooring etc
Bareboat is where they just give you the boat and off you go.
Sunsail at the moment don't seem to be showing their prices for 2025 but I just found an example from Neilson link here to website for specific details for 4 adults and 2 children on a 7 night flotilla holiday in the southern Ionian Islands starting 3rd August 2025, including flights from Gatwick and transfers etc for £917 per person.
That's on a Beneteau 331 with three cabins. If you want something larger like a Beneteau 373 then, yes, you are looking at about £1,500 per person.
"Willing to also pay for two more adults (DB + DSil in exchange for DB sailing is with his sailing qualifications). I have the one day course but it isn’t robust enough for a sailing holiday."
All the sailing companies require the skipper to have at least the equivalent of an RYA Day Skipper certificate and then also for another adult onboard to have sailing experience as well. DB will need to get an ICC, all you need to do is show them your Day Skipper certificate and they will give you one automatically.
Flotilla holidays are great for your first time going on a sailing holiday; there's always going to be someone there at the end of the day helping you with mooring and making sure that everything's ok.
Although I don't know the cost they also do what they call a two week "Stay & Sail" where you spend the first week at a beach club and whoever is interested does some training and then the second week you go off on a flotilla holiday. That will likely work out the same total cost for four people as taking six people on just a flotilla holiday.
The other option is a bareboat charter where you they give you the boat and off you go. That is generally cheaper but you don't get any assistance. Also, most companies like to see that you already have some experience so prefer people who have at least done a flotilla holiday or chartered already.