alder:
The OP asked for advice, I gave it as honestly as I could. However if you don’t tell them what they want to hear they go into attack mode
I did suggest that Sarah could still pursue a worthwhile career and try her fantasy out on weekends to get rid of the novelty value.
Endgame your comment is typical of a good majority of lorry drivers which is why people outside this business treat us the way they do and why many opinions of lorry drivers are that we are thick, ignorant and even stupid. Some people treat us like we are morons dribbling from the side of our mouths and a vacant slot in the skull where a brain should reside. It is no wonder I come across signs with pictures informing us how to climb the steps to get into the cab, Why there are markings where our wheels should be and why when you pull up anywhere 9 times out of 10 the person on the gate has a look of despair on seeing another driver role up to have the instructions carefully explained to him. As a person with a degree and having dealt with people on steering committees, executives and leaders of industry it amazes me why there are not more simplified written procedures to speed queues up when waiting for a load or to be tipped. The reason is that the management of these places have such a low opinion of lorry drivers and view us all as being unable to read a simple document, so they have to draw pictures for us and leave it to the security gate and crane drivers to explain it over and over again 
Sarah, you will do what you want anyway but you asked the question and obviously wanted sanction to follow your pathetic dream over doing a degree and following a real profession. I suspect with your attitude you are already failing in that and have not got the conviction to follow that through. This is why you want to join a merry band of people who can do a simply driving test, follow a sat nav and play their music for pocket money. Being a young person with a life ahead of you I can tell you that I have given you the very best advice for YOU not me as my life is nearly over
If you pursue this fantasy my words will haunt you later in life and you will realise what a chance you had in your grip. You said “bye” but I know people like you will come back and read this. I wonder if your family and friends have advised similar to me and that’s why you came on a forum full of lorry drivers who kid themselves that they are in a worthwhile career and that they are in professions akin to an engineer or mechanic?
Good luck and I hope you see sense

I know this thread is a month old but it was interesting to read 
I am female and I did what Sarah did (well half of it she’s done it, hopefully will do the other half soon) but in the reverse order…
as a young female (I am now 45) all I ever did was driving jobs, first in small van (FEDEX/multi-drop) then double-decker buses in London then trucks (agency followed by international class 1).
then my son came along and I found myself to be single shortly after having him so I had to do my best to look after him and set a good example:
I went back to college to top up my qualifications when I was 25yrs old, from there went onto university and qualified as a Midwife.
Now my son is grown up (nearly 20) and I have realised that this life though its given me the stability and financial security is not the life that makes me happy.
Back in my youth I loved being alone and behind the wheel, I still do! My dream back then was to go onto driving for Edwin Shirley and that is still my dream (well maybe not them, maybe Fly By Nite but in my 20s ES were the only company I knew doing gigs/tours)
so now my son is beginning not to need me so much I am starting to look into pursuing what I originally wanted to do
I’ve raised him, he’s a happy young man my job is done
These 16 years in Midwifery have given me lots of life experience, but so did my years behind the wheel driving…
I don’t actually see truck driving as a ‘career’, well it is not to me, to me it is ‘me’, it is what I am happiest doing.
Now I can go back to it and I have the ‘luxury’ of being a skilled midwife so that any time I need to top up my salary I can do some temping in Midwifery.
Sorry am ‘rabbiting’ on…
I’ve enjoyed reading all replies including Alder’s, which although may seem harsh to some I actually found useful:
one always needs to know all sides of a story and not just the ‘shiny’ side but the ‘dark side’ as well

And if Sarah’s dream is to really drive a truck Alder’s post will not have put her off (hasn’t put me off from going back into it) 
oh: and yes, I have recommended truck-driving to my son as a job but he’s got too much sense and he’s not interested HAHAHAHA (mind you he’s not interested in studying either so maybe there’s still hope
)