For me, (and I'm new here but not to the trade) if the customer if going to such a full extent of refurb, I would definitely have put in a dedicated 6mm cooker feed. Although not completely future proof the likelihood is that most future changes of cooker can then be accommodated.
Also, using the assumption that being a bungalow and your mention of "the rest of the house" I would have opted for the kitchen ring circuit to be on the other RCD to the house not on the same as you suggest. If an issue appears or any nuisance tripping occurs then they will still have power in one area. To this point I would usually try to put the cooker circuit on a different RCD to the kitchen ring circuit for the same reason, i.e. the cooker isolator socket (if fitted) can still be used if the rest of the kitchen is out. I was also always taught to try to balance the load on a split board, having 2 ring circuits and a cooker on 1 RCD doesn't leave much for the other.
Regarding the shower dilemma, if they fail to give you information or a plan, I would suggest that you take a little more control and tell them what they can have given the supply you decide on.
Its fine you keep moving things because they are in the wrong place and getting paid for it, personally I don't like to work that way, and I appreciate many refurbs have to be a bit flexible but to all the other trades, visitors, guests etc it just looks like the sparky put them in the wrong place.
Hopefully I'm not a cute, obtuse knob!!