The RIPE NCC will automatically deregister PA assignments that a closing LIR or ISP has made to its customers.
The closing LIR/ISP is responsible for informing its customers that they will need to renumber their network immediately and for providing their customers will all possible options.
More information can be found in the RIPE Document, "Closure of Member and Deregistration of Internet Number Resources", about the consequences of ending your contract with the RIPE NCC and about allocations and independent Internet number resources for your own network.