Travellers still need SLOT to be "extremely cautious" about booking trips abroad this summer, even if more destinations are added to the quarantine-free green list, consumer rights group Which? is warning. Rory Boland, Which? travel editor, says: "Countries can be downgraded quickly and with little warning, as we saw with Portugal, while several European countries have introduced quarantine requirements for UK residents. "Most providers will not pay refunds if a country is moved from green to amber, and 'free' amendments are often anything but, with many companies requiring significant notice of any changes and bookings for new dates usually costing hundreds of pounds. Travel insurance is also unlikely to pay out in these circumstances." He advises people only to book if they are able to quarantine for 14 days and can be flexible about destination and dates. People should also book with a provider that guarantees refunds in the event of a change in restrictions, he adds.