3 Phase water heater

As a stop-gap I'm using an electric water heater for the Hot Water, and I bought one of these allegedley 3 phase heaters off of eBay (http://www.ebay.co.uk/itm/11-kW-400V-Instant-Water-Heater-Dafi-In-Line-Under-Sink-NEW-/141950067527?hash=item210ce22347:g:R24AAOSwYGFUtDH4), although actually its 2 Phase + Earth with no Neutral at all ???. Note, those advocating dual pole MCBs will be confused.

Before I fit it, has anyone on here bought and used one of these units or something similar ?, and if so, any tips.