Vaseline Sheer Infusion with Stratys-3. All 3 available (Vitamin Burst, Mineral Renewal and Botanical Blend) at £2.99 each at Savers.
Next cheapest is £4.99 at Boots.
I got sent a free sample in the post and it was so good that I decided to buy it (you get a 50p off voucher with the free samples if you can still score one), so actually only paid £2.50 - half the price you'd pay normally in Boots!
Before I tried this, I thought all moisturisers were the same. When using this one, I can still feel my skin is moisturised 1-2 days after using it!! Not only that, but because it works so well, you only need to use a very small amount each time you use it, meaning this will last you ages compared to the normal vaseline range. Definitely worth a try at this price.