Housing brand confusion

I had a ikelite housing in 1983-knobs bound up at depth-it was to buoyant -I;m sure they are better now but after 3-5 aquaticas and a the same with Subals I would never go back to plastic. 

Just get a used aluminum housing and you will find it does it all very well and the cost is less in the used market.

I consider ikelite entry level on the way to a better housing ,save yourself this step

I will add my perspective as a long time Ikelite user. There is a lot of good information that has been given and I don't envy your decision as a budding UW photographer. 

My first Ikelite housing was for a Canon AE1 Program. It was a rather bulky and cumbersome housing. I never was able to actually use it much. My next was a housing for a Sony CD camera. That one I used a good bit and worked reasonably well. Next was a Canon Rebel XT. I got some good shots with that one. A bit better than the AE1 housing as far as usability. It worked just fine and I never had an issue with controls underwater. Deepest was maybe 80 or 90 feet. Next was a Canon 7D. Very similar to the XT housing and worked just fine. Next up was a 5D mark 3. The housings had evolved some at this point and had a different tray and handles. Just recently I picked up a new open box housing for my R5 from eBay for $400 US. A pretty shocking amount for a $1700 housing. So yes, resale isn't that great. But seeing as I still have my last two housings I'm not concerned about resale. The new R5 housing is advanced a bit more and comes with a vacuum port. The controls are a bit better but I still don't have controls for everything and some of them are awkwardly placed. It does have an easy to use back button focus trigger though. That is the nature of the plastic box. I find good cost to value ratio with Ikelite. They have great service although I am not sure about the UK. The TTL systems they offer work very well but that requires using their strobes, but that is ok as they are very good as well. 

I certainly would like a Nauticam and I have looked at them several times but as much as I enjoy taking pictures underwater I struggle to pay many thousands more for what will probably result in just slightly better photos if I could even tell. 

If you could find a second hand Ikelite system it may be a good way to get into the hobby and decide if you like it. 

Thanks all, these are some good points of view!