Cats, you have 4, 2 in the headers (pre cats) and 2 post cats. You can remove the post cats without issue, but the header cats you need and these are the ones that can break up.
The timing chain I would change as its £100 for the chain, tensioners and guides, but the combined oil/Water pump is silly money at a grand. Dont know how much the scavenger pump is but is wont be cheap.
You could always just send the engine to David Askew and he will go through it, replace the shells ets for about £2500, or just not worry about it, and if it were to go POP, you can get an exchange for £2500 anyway.