If you are due to go on a package holiday, then your booking should be financially protected by a scheme such as ATOL. You should have been given an ATOL certificate (or similar) when you booked your holiday, which includes details of what to do if the company goes into liquidation. If the company does go into liquidation, customers should visit the Civil Aviation Authority’s (CAA) website for guidance.
If you only booked flights, these may also be protected by a system such as ATOL, although it is less common. If you do have protection you would have been given a certificate (or similar) when you booked your flights, which includes details of what to do if the company goes into liquidation.
If you purchased some or all of your flights or booked your accommodation separately using a credit card, you may be able to arrange a refund from your credit card provider or PayPal. You may also be able to claim on your insurance, but this will depend on the level of cover you have in place and usually your excess will be deducted from the amount to be repaid.