Please help, my passport application was declined for an unsatisfactory photo and I won't have one in time for my coach trip through Europe on Tuesday. What can I do?

I'm due to travel from the UK to Hideout Festival in Croatia this Tuesday with Big Green Coaches. However, having sent off for a replacement passport weeks ago I found out just yesterday, after ringing the UK passport agency, that my application has been declined and that the letter with this information was only sent on Thursday this week. I am told I cannot send another photo until I receive this letter. I am also told that I cannot use their one day service because my application is ongoing and I cannot start another one.

I am at a loss as to what to do. I'm not sure if I can sell my ticket at such short notice nor if I am even able to because ticket holders must show their ID upon entry (I emailed Hideout about this weeks ago but received no reply).

I have read online that neither the UK nor Croatia is part of the Schengen agreement which allows EU citizens to travel freely across borders. Therefore I am required to carry a passport when travelling to and from these countries. However, I am told that border control is particularly slack when it comes to coaches, cars and trains so there is a chance I could get through albeit slight. I have also read anecdotes online of people who were let off for not having any documents on them when crossing these borders.

At the moment I have the following possible solutions:

1. Sell tickets, don't go.
2. Risk travelling by coach without a passport but with all other forms of UK identification (Driving license, National insurance number, old passport)
3. Drive to London on the Monday and plead for a one day service to get a replacement passport.
4. Request a temporary travel document from the FCO. (Am I eligible for this?)
5. Try to get a passport by the end of the week and fly to Croatia in time for the weekend.

Please reddit, what should I do?

TL;DR I don't have a passport and need to get from the UK to Croatia in time for 29 June

EDIT: Grammar