Glad you've got it sorted. As for the legality of it all, I'm not sure what is right as I was put on an injection course run by Rossdales in my last job and was shown and practised intravenous injections, not that we had to do it as part of the job thankfully and would not really want to have to do it either. When intramuscular jabs are needed it is common for vets to use their discretion as to whether the client is up to the job. Penicillin is not a nice one for horses, but Excenel is even worse, they certainly react to that one more.