The "big" HGV training companies I wouldn't touch with a barge pole if I'm honest, you would be much better off going to a local training company with a more personal touch. I know in your situation it's a bit too late for that unfortunately.
What part of the driving/working hours regs is that you are struggling with specifically?
https://www.gov.uk/guidance/drivers-hours-goods-vehicles
if you give that a bit of a read through, it should help cover most of the basics. It can be mind boggling at first, but you will soon get to grips with it.