I'd suggest that you check EA byelaws for the river that you're planning to fish unless you wait until June 16th.
I didn't take that into account, I had my fish as "accidentals" during the coarse season on the; Test, Irfon, Wye and Itchen. I don't know if the flavouring has a particularly beneficial effect as most game fish love it anyway.
I've had: Grayling, Rainbows, Sea trout, Salmon and the odd Chub on corn, they love it. Not bad results considering that I hadn't fished any of these rivers up until a couple of years ago. I also fished an "Any method trout fishery" in Belgium and they were crawling up the rod for it, over forty rainbows in one day was my best effort, you weren't allowed to return any fish and had to pay for every fish you took, it cost me a flipping fortune.