I'm in the exact same situation. I had to cancel due to covid and was only given the option as a travel credit. This credit is only half my money, the other half is a friend's.
I have to book by 21st Dec 2021. However, I will be unable to travel next year - If I could, how is it even possible to try and guess when and where I could go on holiday next year. It's ridiculous when a pandemic is still happening. So, I'm stuck with this expiring travel credit.
I had planned to try and use it this year but if covid doesn't improve and I have to cancel, I heard I wouldn't even get the travel credit back and loose all £550 of it.
I'm so stressed and upset by it.
Edit: My email states " All trips must start by Dec 30, 2021"
So it's not even booking I must book a holiday for this year.