Jeepers Colwyn, as much as I feel sorry for your predicament I'm astounded that someone of your intelligence/awareness etc. could book with this awful organisation. (20/20 hindsight - I know).
They moved their base to Palma, Majorca in 2013, thus excluding themselves from ATOL. To the best of my knowledge, they were never members of ABTA.
The CAA recommended not using them in 2013 despite their assurances that Spanish laws would provide sufficient protection.
Hopefully, you booked on a credit card - perhaps you can recover your monies.
Thankfully, your flights are not booked through these charlatans and I hope that your hotel can help you out.
My neighbour and her two children are amongst a 30 strong party booked to go to Spain in August with these people. All flights/hotels/transfers were prepaid.
Lowcost's problems were apparent long before Brexit!
All the best, Colwyn.