We got a large garden shed/cabin for our back garden and have the pool table and dart board and bar out there. We did look at shomera but they were so expensive. We got a 26ft x 15ft shed from O'Briens Timber Products and it is fantastic. My husband is an electrician and good at DIY so he has wired it, put heating in, put down a wooden floor, and put a sink/bar counter in. He has insulated the walls and I have to say it looks great.
However, if you are tall as in 6ft plus I wouldn't recommend these as the internal roof beams would annoy you. Also, the windows don't open so I would imagine it gets quite hot in the summer. But it was a fantastic investment and really looks the part, so much so that we have visitors every weekend!
I know you didn't want to go down the garden shed route, but with a little bit of work and imagination, they can look great and are definitely much cheaper than Shomera.