My advice is to get your medical and theory tests out of the way first.
When you apply for your provisional licence make sure you tick all the boxes for C and D. This gives you a provisional licence for both the lorry and the bus.
Then get your mod 1a and 1b done for both C and D. The bus and lorry theory tests are separate, so you will do 1a and 1b twice, one for the lorry and one for the bus.
This is all relatively cheap, if you do it all yourself. Maybe £45 for the medical and £100 or so for all four theory tests. I don’t have up to date prices.
There’s an official DVSA theory test book and a hazard perception DVD that you can use for both the lorry and bus module 1a, module 1b, and module 2.
If you get cracking, that shouldn’t take you more than about 6 weeks. Then book your bus and rigid lorry tests with the forum sponsor.
After you have your cat C and D, book your C+E test. That will also give you D+E.
By June, you should be ready for the summer rush. Loads of agency work in June, July, and August as this is when many of the drivers take their summer holidays.
It’s quiet each year during January, February, and March. It usually picks up after Easter.
With lorry driving, make hay while the sun shines.