We are contacting you regarding a past Prime Video purchase(s). The below content is no longer playable on Prime Video.
In an effort to compensate you for the inconvenience, we have applied a £5.99 Amazon Gift Card to your account. The Gift Card amount is equal to the amount you paid for the Prime Video purchase(s). To apologize for the inconvenience, we've also added an Amazon Gift Certificate of £5 to your account. Your Gift Card balance will be automatically applied to your next eligible order. You can view your balance and usage history in Your Account here:
From dealing with their support in the past and stuff they've accommodated, I wouldn't be surprised if you could just ask them to do it for a small amount like that. If you do a web search, you can also find a lot of information and people claiming it's possible to do stuff like transfer it to a Paypal account, etc.
I haven't tried to do that personally, so maybe it really just isn't possible. It's still only something that will affect someone that's never going to spend money at Amazon again, right? If I'm going to spend $5.99 at some point, it's effectively the same as a cash refund for me. If I'm going to spend $10.99 at some point it's almost the same as getting double the refund, since I would have spent cash instead in those cases.