I also would feel better with the bottle outside. When you sell your house you will need to have a certificate anyway. You might as well do it now to be safe.
I once managed a house with a gas stove which was installed with a certificate. Tenant reported gas smell. I had to call this guy back twice until the leak was finally sorted.
On the other hand a tenant wrecked the hose pipe between bottle and pipe. I just replaced it myself. No leak. Maybe I should change jobs and become a gas installer, ha ha.