Buy The Underwater Photographer by Martin Edge, 4th ed. Then read it. As you practice/learn more, read more or read again.
Get in 20-30 dives with no photo gear before considering taking it. Then start using it on dives with easy dive conditions and reasonable visibility.
Consider practicing diving with photo taking in a pool. You can learn quite a bit about your system this way and it usually costs little. You can learn about your lights and how much light they offer you in perfect conditions in the pool.
I like fiber optic triggered strobes and those work with your housing.
People in the UK can likely provide better insight for lighting local diving.