The fishing round Hellevoetsluis is brilliant but I’d be careful of fishing the Voorne in October as you will probably only catch roach and maybe the odd resident Bream as the Bream move in around end of March for 2 or 3 months.
First thing I’d do when i got there is go and see Mario in the tackle shop in the town centre by the swing bridge and ask him the best places to go.
he’s got a website http://www.de-catfish.nl/eng/witvissen_eng.htm so you could mail him for any advice on what you need to take before you go or he could sort your baait for you. he speaks really good english and it’s a well stocked tackle shop.he’ll sort licences and everything for you
I’ve never been at that time of year only in April and May but there will be places to go and catch plenty of fish.