Yeah, about 12 x 8 or 14 x 10 is the biggest I could go but I've thought about using an enclosed Gazebo for extra space in warmer weather and serving from a side hatch. I'm on that Pub Sheds Facebook page for ideas and everyone says build as big as you can.
Nifex in West Belfast apparently will fill any bottle but I haven't used them. I've a corny set up with nowhere really to serve them other than my brew fridge so I bottle mostly. I really need somewhere, hopefully next year.
Thanks for the help.