How old do you have to be to go on holiday unaccompanied by an adult?

Basically, im in my last year of school and my friends and I are making use of the extra time off by doing something fun! We really want to go on holiday with each other, we realise Spain and other countries abroad will be out of the question as we live in the UK but even if we go to somewhere like the Isle of Wight that will still be good like staying at a holiday park or something although we’re not sure if any of the holiday parks accept groups of (approx 5) 16 year olds with out an over 18 there to supervise, my step-dad says we don’t stand a chance but its something we really want to do, so I really need some help!!!