The EU guidance on this says:
”
- If the airline does not comply with its obligation to offer re-routing or return under comparable transport conditions at the earliest opportunity, it has to reimburse your flight costs.
- If the airline does not offer you the choice between reimbursement and re-routing but decides unilaterally to reimburse your original ticket, you are entitled to an additional reimbursement of the price difference with the new ticket (under comparable transport conditions).”
Nowhere is it stated there are any exemptions for low cost airlines etc. This would imply that if Easyjet can’t reroute you then they need to cover the additional costs for the new ticket.
https://europa.eu/youreurope/citizen...t-cancellation