An A level means the AS + A2, yes
A one year course will do both parts in a year, which can be a lot of work
it might be worth checking the format - some colleges will put you in with the AS and A2 groups so that you start both halves together - this can be confusing if some of the A2 bits build on the AS stuff that you haven't done yet, so you may need to do extra work. Other 1 year courses basically teach the AS in just over a term and then do A2 in a similar time - at least then you're doing everything in a proper sequence