Unsafe self-catering accomodation - what are my rights?

Hi all,
Any advice gratefully recieved.
I booked a self catering apartment for one night with Booking.com
When my family and I arrived at the appartment we uncovered more and more issues in our short stay - fundamental issues of safety, repair and hygiene.
I've raised these all with Booking.com who state the accomodation are unwilling to provide any refund, and seem to be taking the line that it is not their responsibility. They are only willing to provide a 25EUR goodwill gesture, less than 20% of the cost of overnight stay.

Issues as follows:
• Dirty floor - blobs of brown gunk
• Dirty wardrobes (hairs and dust – see photo below – not nice!)
• Hairs and dirt in double bed, sheet was creased and had yellow stain (sheets not changed?)
• Towel ripped
• Kitchen worktop cracked and swollen next to sink
• Kitchen bin dirty, with no liner
• Brown gunk smeared on doors and skirting boards
• No fire extinguisher
• No fire blanket in kitchen
• No fire evacuation poster
• No fire escape signage (this is a 3rd floor property)
• Smoke alarm not working
• Hot water not working in taps (shower did work)
• Bathroom sink plug didn’t work
• Curtain rails broken in at least two rooms
• Dirty curtain in main bedroom
• Towels thrown in corner of bathroom (not changed?)
• Dirty walls
• Dirt behind doors
• Front door not shutting without key (meant that key had to stay in door)
• Front door security chain broken
• Electrical switch cracked in kitchen
• Black mould in shower tray sealant.
• General smell of damp.

Do I have any recourse here?

In spite of raising the fire concerns, booking.com are refusing to take that side of it seroiusly - I advised that they should stop advertising the property until the fire stuff was fixed - they seem unwilling to do this, I'm properly concerned that if there ever was a fire there someone could be badly hurt.

Advice would be much appreciated!