Worried if I get assessment date letter too late

I had a letter from Capita saying they had received my form and they would inform me if I needed an assessment and I know it can take a few weeks but after reading of people getting letters after their assessment date or very late I am worried in case I don't receive a letter if it gets lost in the post or I get the letter too late. I phoned the progress line to ask about the status of my claim and they just confirmed they had received the form and suggested I phone Capita.
I'm a bit nervous about contacting Capita but is this the only way I will be able to find out? Don't the progress line see the information about assessment dates on their system?
I need to have a home assessment so want to have a chance to sort this out once they decide if I need one or not and I'm constantly worried in case an assessor turns up without me knowing beforehand if I don't get a letter of an assessment date in time. I don't want to phone Capita but do I have to or is there any other way?