The place is easyish to find (with sat nav and street view

). Quick friendly service. I got 2 5kg bottles for £35 each (one's for my mate). One of my bottles turned out to be older than me and not tested since '94

so I scrapped it. I'm now an owner of a new BIG bottle that'll last me a year probably and a backup one. I'm sure it I'll have a reason to come to Birmingham at least once a year.
Thanks everyone for the help.