I have both the HEPA air purifier and energy recovery ventilator from these guys: http://purifresh.com http://purifresh.com They work pretty well (keep my wife

I have both the HEPA air purifier and energy recovery ventilator from these guys: http://purifresh.com http://purifresh.com They work pretty well (keep my wife's allergies in check) and are simple but well-constructed units. Edit: but they are US based so shipping may be equally expensive to the UK.