According to Martin Lewis: Check your cancellation rights – can you cancel for free? If the travel company/flight operator have cancelled, then you are entitled to a refund, but you may be offered a voucher instead.
Which? advise you not accept the voucher, as it is unknown if you will be able to use this in the future. If you wait for the foreign office to say you can’t travel, then most insurance companies will cover.
Which? has up to date info on its website, with lots of questions and answers dedicated to holiday questions: https://www.which.co.uk/news/2020/04/coronavirus-what-it-means-for-your-travel-insurance/