Frames
I've attempted to offer framing in the past but delivery & insurance stopped me providing the service.
However if you want a frame nice frame, that fits like a glove, I can highly recommend the Nielsen Pearl. Its super easy to clip your poster into this and it looks great. I have them all around my house now!
Available on Amazon (Prime) in A3 or A2.
If you want your artwork mounting I would recommend getting down to your local framer. They will do a great job and line it all up nicely. I tried a few myself and was surprised at how much hassle it was!