I know how you feel, my dd is now 3y 5mths and we went through febrile convulsions for a while, we were told its not the actual temp that causes it, (even though dd was 41.6) but the speed of how the temp goes up, we were referred to Alder Hey childrens hospital in Liverpool which is a long way from where we live, and we were very frightened, the specialists there said dd would grow out of it, and this is whats happening, as she gets older she manages to control her temp better, I did find that calpol on its own was no use but ibuprofen was great, and we could still use calpol inbetween.
One thing I will say that is important is check you are giving trhe right dosage with these medicines with your gp, I didn't realise until my dd was taken in hospital after a convulsion, that her bodyweight was not enough for the age guide, and I had actually given her more medicine than I should.
We had a poorly spell at xmas and I got her weighed again with gp and found that I was "officially" allowed an extra dose in emergencies, but not to do on a regular basis.
I find that illnesses that children can normally cope with will bring temps of 40+ in my dd and its easier to control this at home with medicine, a fan, and tepid water being sponged over her.
Hope this helps.............