I think its always important to get emergency help (be it ambulance or seeing a doctor immediately) if your reliever medication is not helping when you are having an asthma attack as it is best to be on the safe side.
Even though there have been occasions when they haven't given you treatment I assume it would still be important to get it checked out as stridor/wheeze can be caused by other things or there may be another reason as to why you got unwell such as a chest infection.
Please don't feel like you are wasting their time, breathing difficulties should always be checked out if in doubt.
I have a question for you guys, when I have an asthma attack I get stridor rather than wheezing but I sometimes do get both...So anyways, I have been in a&e with this before and I was wondering when I should like call an ambulance and when I shouldn't cause I have called them in the past and they never gave me treatment and I hate wasting their time as their is most likely someone else much more critical needing seeing to and there I am fine and they came to my call rather than theirs.
If you could give me any advice at all it would be very much apprciated