Beach/lakeside holiday for four 18 year old sensible girls - where to look?

[Madcats]

DD has announced that she and her friends want to go away together for some summer sun before heading off to university (and apparently it has to be 1st week of August). Warm and sunny, but not baking hot. Not Portugal (no idea why). Near a beach or lake and happy to self cater, but equally happy with some sort of meal plan.

They all do part time jobs, but budget is probably £500/each (I am thinking fewer days would be better than rougher location). We can get them to Bristol/London airports or they can Eurostar.

I thought about Centre Parcs/Duinrell style places in Europe but min age seems to be "at least 1 person aged 21".

Are there any companies that cater for <30's? I know Intrepid do (but too expensive).

I feel like the vibe would be a bit kids focused st those places. I’d encourage them to consider a youth hostel. Italy has some fantastic youth hostels, maybe lake como? They could probably get accommodation for around £20 pppn.

Thanks for the tip. DD has stayed in plenty of Youth Hostels here and abroad, but I'll look to see whether any are close(ish) to a train station.

Caravan / camp - Eurocamp? It’s a tight budget for a week

One of my sons went to Cinque Terra in Italy for his post-A Levels holiday with mates. They rented a basic villa (no pool, but big enough and comfortable and they could walk to the beach), flew with Easy Jet for peanuts, and used the excellent train service for getting around while they were there. I can't remember how much it cost, but it wouldn't have cost more than £500 each or some of them wouldn't have been able to go.

We went to Barcelona at that age, post A-Levels.

£500 for a week in August is very very tight.