Cheers John! I'm a bit of a bulk buyer, the logic being that the stuff is cheaper and I can sell the rest if I don't use it. Very pleased with myself yesterday as I bought 6 HF204 filters for the Kwaka at £26.99 (about £4.50 each). Even better though, was that there was a promotion on Ebay which took 10% off, so a little over £24 for the 6 (free postage too), I love deals like that. Each filter came out at £4.04 each

Now I'm looking to do the same for the HF153s?
From what I've been advised on the Forum, I wouldn't worry about blockages anyway. It takes a lot of cack to block a filter, then there's the bypass valve which basically means the motor would be running the way it was originally designed.
My filter arrangement means I can put in a variety of filter heights, but not widths as it sits between the engine plates where the ski slope usually goes - seems to be working extremely well at the moment!