LB BCGA Guidance Note 2 "Guidance on the Storage of Gas Cylinders in the Workplace" Revision 4 (2012) - I think it's a free download. 3m separation between LPG and other flammable gases, 3m oxygen.

This snippet of information can also be found in HSG139 http://www.hse.gov.uk/pubns/priced/hsg139.pdf

We have absolutely no outside space in a city centre location but, must have oxy-acetylene on site for repairs of a particular process. Elimination (removal fro site) is not an option. So the kit, with 3 or 4 LPG bottles is stored together in one largish cage in the open air at roof level. I appreciate that the distance between cylinder and mixing of gases rules are not complied with, but the alternative of keeping the gases within the building (as they used to be stored) IMHO creates a far worse risk of fire and explosion. Views???