Oakley store in Covent garden is the flagship UK store - 2 floors of Oakley eyecandy! If your visit coincides with one of their sales you will not be disappointed!!
1-4 KING STREET COVENT GARDEN LONDON WC2E 8HH Phone: +44 (0)20 7395 6070 Email: OStoreLondon@oakley.com
Prices are generaly the same as the Oakley UK website but their sale price can be upto 50% off.
There is indeed a loyalty card. I got one the last time I was in the Cheshire Oaks Vault. It gives you money off at the till then they send you a voucher from time to time and I think from memory you get a voucher on your birthday too. I got chatting to the sales guys in the Vault because I was wearing custom Flaks and I happened to mention I was on the forum and the guy gave me the loyalty card.
Scroll to the bottom and you'll get the info on the loyalty card.
The Vault at Cheshire Oaks is ok if they have what you're looking for. Prices aren't that much cheaper than the likes of Shade Station. I think there is also a Vault in York and there is a Vault in Southampton which does have good prices.
Edit: Cheshire Oaks are on facebook and post when they have sales or new stock coming in
The UK flagship store is hit and miss. Sometimes they have stuff before it's official release date, sometimes they don't have any stock and/or have never heard of stuff that's widely available from other dealers and on the Oakley website. Their hands are tied with this, Oakley HQ randomly send them stuff, with no notice about what is coming and the store can't/isn't allowed to order stuff in specifically for customers. They onyl knwo what they get when they open the delivery box. It's a bizarre way to run a flagship store, let alone any store. There are some good staff in there, and some not so good. Probably best to avoid weekends as you'll get the part time staff who don't really know the product. Prices are as per the Oakley website. UK exclusive stuff (such as t-shirts, caps, lanyards etc) is on display right as you walk in. Upstairs is the custom bar.
ShadeStation don't seem to do as good a deal as elsewhere anymore.