I am looking for tips on how to spend some Avios.

I am based in Sweden and I am a frequent flyer within Sweden and Europe. This, in combination with a few trips to New York and use of a BA credit card has netted me about 210 000 Avios. Given that they have butchered the BA card in Sweden I will move over to Star Alliance so I am not going to be generating much Avios in the future.

I also have a BA Companion Voucher that expirers the 10:th of July 2016.

My plan is therefore to take my girl on a trip somewhere during the spring/early summer. I am looking for a longer flight non-stop somewhere warm (preferably somewhere where we can jump another plane and get to a place where one can swim and have cocktails on a beach). I would like to travel in first, preferably in the A380 as I have not done so but it is not a must as long as the first class product is solid.

As this is my first time booking a reward flight I am looking for some inspiration.
What would you guys do?

I also have a few questions that I have trouble finding answers to.

1. If I book a reward flight for me and my girl with a companion voucher can I change my companion? I am asking as my GF have a job where she can get called in with rather short notice and it that happens for when the trip is planned it would be good to be able to bring someone else and not waste the voucher. I know I can change the dates but after the 10:th of july the voucher will not be valid anymore and that will not be an option.

2. Using my voucher the trip must start in Sweden. If I want to fly first out of London, can I book the leg ARN-LHR in Economy? Seems like a waste to spend extra Avios on Club Europe for this short jump.

Thanks in beforehand!