Just a brief word on this.
If you have a friend who has access to a Cash-and-Carry outlet, check with them first before paying some of the prices called for by some eBay sellers.
When I first wrote this, I said that a recent check with a friend of mine indicated that Costco were selling a 6-pack of BRITA Classic water filter cartridges for £12.00.
Seven months on, I've just returned from the local Costco where a 6-pack is £11.99, or £14.08 including VAT. That's about £2.35 each.
And don't forget to factor in the P&P! As I'm updating this, I notice that there are a number of 3-packs on offer. The P&P ranges from £1.60 to £6.56!! I've weighed 3 cartridges (in a box) and it was just over 370 grams. Top postage should be £1.49 plus 68p for Recorded Signed For plus something for the packaging and maybe even something for travelling to the nearest Post Office and back.
As at 20 February 2007, there is actually a seller with an open auction for 6 cartridges who expects to charge £7.99 for P&P. Either he/she is a fool, or they think you are. Don't be conned!