Be careful with the screen protector as most advertise as SE/8/7 compatible when the SE's screen is ever so slightly curved, you end up getting a halo effect. You need one specially designed for the SE. I bought mine from Amazon, a company called Omoton, they fit perfectly and come with a little framing tool to help application. I wouldn't go to a shop as most are unaware of the sight difference.
As for the case, I use a Spigen rugged Armor, which despite the name is quite sleek. I also have a Spigen Tough Armor which is more protective but bulkier and a Ringke Fusion X which is probably the most stylish but it left the faintest scratch on the back. All three were Ł14 or under.