nowt to do with me but question has arisen about whatto do with a brake linbe that passes trhough a metal bulkhead.

Is using a rubber grommet ok (does SVA say anything about this?)? And how esle to do this? (i.e., is a bulkhead connector the only acceptable way and should adding another join be a concern).

Rubber grommet should be o.k. That's how mine are done on my van through the front inner wing.

Don't know about the legalities but I've done both and think that the bulkhead fitting is a better 'engineering' solution

Best bet is to see how the OEMs do it and try and do the same yourself.