I am a bit confused about the wording that says that you do not have to take the theory test to upgrade within the same category (“If you have previously already passed your LGV theory test in order to acquire a C1 licence, and are “upgrading” to Category C, then you will not be required to re-tak the LGV theory test again” 1Stopinstruction.com) and whether that applies to drivers with Grandfather rights. This is for test not CPC. Does that only apply to people who actually took the theory test to pass their C1 or as I already have C1, being old, can I just do practical for moving on to Cat C? Just being hopeful really as I suspect I know the answer!
So to shatter your hopes but you will need theory tests so you can progress to CAT C. If you had C1 by having passed a specific test for it, you wouldn’t now need a theory.
When it comes to practical training you can get credits towards your driver cpc from the practical provided that your chosen trainer has approval for this. So do, some don’t.
Hope this helps, Pete 
Those with the free pre 1997 LGV C1 only passed a basic car test to get it so did not pass a specific HGV test to get it as it then was
I passed my basic car test back in 1979 in a 7.5 tonner (now LGV C1) but that did not give me LGV theory rights for LGV C
That’s because there was no theory test in 1979. But anyone who has taken a theory test for C1 and subsequently passed C1 practical wont need a theory test for C. I think that was the point, but I stand to be corrected if I’ve misunderstood the OP.
Pete
Peter Smythe:
That’s because there was no theory test in 1979.
But pertinent questions in relation to the vehicle test being taken were asked if I remember correctly 
To get category C added to your driving licence you have to do module 1 and module 3, as you didn’t take the theory test for your category C1. To book module 3 on the gov.uk website, it will ask you for your module 1 pass certificate number ie. the theory test pass certificate number.
To get a DQC (Driver Qualification Card), so that you can drive a lorry professionally, you have three choices:
Choice One: Do module 2 and module 4. This will keep your DQC valid for 5 years.
Choice Two: Do 35 hours of CPC. This will keep your DQC valid for 5 years. (Most training providers seem to recommend this route because there is no test so you can’t fail.)
Choice Three: Do module 2 and module 4, then do 35 hours of CPC. This will keep your DQC valid for 10 years.
Note: Only drivers who had category C1 on their driving licence before September 2009 get the option of just doing 35 hours of CPC instead of doing module 2 and module 4.
Thank you for your replies. That has cleared up that point and as I suspected I will need to complete the theory test before going on to training. Best get studying!
Cheers
H
Free Official DVSA Practice theory test for large vehicle drivers (1 of 2)
safedrivingforlife.info/take … e-test-one
There are 50 questions on practice test 1, and another 50 questions on practice test 2.