Hi Matthew
Don't bother with the screwfix one, I made Enquiries to there technical support department to find out they don't have one anymore, so they gave me the number of there suppliers, after a long conversation with them it worked out better to buy from some were else, but buy your filters from screwfix. I cant remember what was said as it was some time back, but if you phone screwfix head office here in Yeovil somerset, they will give you there number and you can speak to them yourself and see what i mean.