plugwash said:if your master socket is a nte5 then you might be interested to know that http://www.clarity.it do a special version of the splitter faceplate that has terminals on the back for the unfiltered signal
ADSLnation also do a microfilter faceplate with terminals on the back for the unfiltered signal:
http://www.adslnation.com/phpapps/catalog/product_info.php?products_id=90
As far as I can tell it is more-or-less the same as the Clarity.it one, and the choice comes down to price / stock-level / minimising shipping cost.
The Clarity.it one is £17.50 with £2.50 shipping so £20. The ADSLnation one is £15.99 with £1.50 shipping so £17.49.
The microfilter in this microfilter faceplate will be a good one compliant with the relevant requirements (BT SIN 346). However it will be a passive filter, and I don't reckon it will be quite as good as the active XF-1e circuit.
See here for a comparison of microfilter innards:
http://www.adslnation.com/support/filters.php