Free £15 spend (I got some bits from next) lots of retailers including Amazon so could get an Amazon voucher!
Sign up using the referral link
Verify details, confirm email and add debit card
Receive 1500 points (£15)
To spend the reward -
Pick a retailer from the app/website (you can also search for them)
Make sure you click to turn on use rewards for next purchase at the bottom of the screen after you select the retailer
Zilch generates a virtual card for you to use which you input the details at the retailer to spend the £15 
customers.payzilch.com/signup?inviteCode=Pe5qwv