Just found this on the Tesco clubcard reward site.
Allowed three perks per clubcard so £15 free credit!
Terms and conditions
There is a maximum of 3 credits per customer account.
Your redspottedhanky £5 credit can only be used to book train travel in the UK only. It cannot be used against European travel or Events on the redspottedhanky.com website.
This offer is for direct bookings made via www.redspottedhanky.com and the £5 credit is not combinable with Clubcard rewards e-vouchers or any other discount, offer, scheme or promotion and cannot be exchanged in whole or part for cash.
Extra perks cannot be transferred, bought, sold or in any way traded.
This extra perk may be withdrawn at any time.
Please note: Clubcard will operate a fair usage policy for extra perks. To ensure that all Clubcard customers have a fair chance to receive an extra perk, we will monitor to ensure no one customer is putting through an unreasonable volume of extra perk requests and take action to limit this if necessary.