DLA help please

hi guys I’m new to this group so not sure if this is the right place to post apologies if not! I just got my 5 year old sons diagnosis “server autism spectrum disorder “ we currently receiving high rate care and low rate mobility but we strongly think he should receive high rate mobility and would just like to find out some advice we never appealed the decision at the time as we didn’t have a diagnosis does anyone if now we have the diagnosis will it help us in getting the high rate mobility for him? Any help would be great tia x