Brita Elemaris Cool White Promo Pack With 4 Maxtra Cartridges at £6.25 (RRP £24.95 amazon).
This is my first post so please be gentle.
Lookout for this filter jug with 4 maxtra filters in store at Tesco.
The same filter jug at Tesco Extra with just one filter is also on sale at £14.97 (crazy). You can't even get the filter on their own at this price.
You will need to look in the reduced.discounted section of your Tesco store and I suggest you get the price check before you pay.
PS The shelf I found the filter jug still had a shelf label with £24.95 with discounted.