Seat selection fees are in theory non refundable, even in the case of upgrades.

However you can try calling to ask - I managed once to get my paid seat selection refunded when I upgraded with Avios, though this was apparently because the call centre agent incorrectly agreed to it initially so they had to follow through with it. It’s worth asking.

As for if it’s worth it - at that price for me yes it is worth it, but of course that’s very subjective. WTP is noticably more roomy and easier to sleep (especially in the bulkhead) and the cabin tends to be quieter.