You should be ok if you are taking ventolin. I have asthma and my ME said that as my asthma was bought on by exercise and cats and was mild I was ok. I was put on becotide by my GP and am now waiting to find out whether that is ok.
Best thing to do is go for your Class 1 and see what happens. I believe that if your asthma is well controlled you are ok. There is some info on The CAA website.
Good Luck.