With the greatest of respect BSpare, do you not think that companies the size of Hargreaves and TP would just go directly to source if they found out you were simply a distributor? Bearing in mind Wolseley have the power to order 1000 at a time and stick them into stock, I think your supplier might just say hang on were in bed with the wrong company here.
When I was in Beijing two years back I was offered a spirovent (for trademark reasons obviously wasnt a spirovent) for £8 per unit and that wasnt even based on me ordering any significant volume, suprisingly no one would touch them with a barge pole based on that should something go wrong with a magnaclean or TF1 you know there is a huge company behind them to come out and fix/replace the unit and cover any costs associated from potential carpet damage etc. In your case should one filter bring down a ceiling, you will be liable for paying for the damage.
I don't want to put the dampners on you too much mate but Ive seen people fall at similar hurdles with other products and its cost them their original, profitable, business just to pay off the debts associated with bringing a product to market. Do yourself a favour and call Chris Adey or Fernox and ask them if they think it will work before risking your career on something.