The regs say where reasonably practicable,if for instance the meter was external and the gas pipe went under floorboards to a boiler and then teed off elsewhere this is where i would bond to,by the sounds of your post you must be having a bit of bother with access to bond,main bonding in the regs should have some form of diagram on certain scenarios so we can meet the requirements,there is an niceic snags and solutions book on earthing & bonding,i dont have a copy but expect it would be in there.ive just finished off a bottle of red wine and hope i have not made any spelling mistakes hiccup lol