See your avatar? That's what you'll be doing in the ops room as a warfare specialist. When you're not doing that you'll enjoy being on the upper deck chipping and painting. Enjoy keeping the ship clean and tidy.
It's not a cookie jar where you can pick and chose what you like when you like if you decide to change your mind. You need to speak to your AFCO soonest. WS and ET(WE) are very different jobs. You have to be found suitable for them and this will involve another interview to investigate your reasons for change. You cannot change your branch when you join HMS Raleigh. So if you're having doubts, do it now.
You need to make your decision now. If you are having second thoughts then let your careers advisor know on Monday. But to back up what has been said earlier, you will need to do some of your selection again. You also need to understand that once in it's very hard to change jobs, so make sure you are one hundred percent sure on your choice. The difference between ET (WE) and Warfare Spec is vast, what do you want out of your navy career? Also think about what you can do after your navy career.