PlayStation currently has promotions on PS Plus subscriptions as part of their Days of Play festival. You could use these PS Store wallet gift cards to redeem a PlayStation Plus subscription using denominations £10 to £200.  If you are a ShopTo Silver or Gold member you'll get even more discount.

Gift cards with 15% off

• £10 for £8.50
• £15 for £12.75
• £20 for £17
• £35 for £29.75
• £40 for £34
• £45 for £38.25
• £50 for £42.50
• £70 for £59.50
• £80 for £68
• £84 for £71.40
• £90 for £76.50
• £100 for £85
• £120 for £102
• £150 for £127.50
• £200 for £170