The London side led 6-3 after two quarters and 8-5 after three before Lancaster staged a late recovery. Main scorers for Poly were Chris Icely (4), Ciacomo Cupido (2) and Chris Brown (2).
In their second match, Poly led Manchester 4-2 in the third period but eventually settled for a point in a 6-6 draw. Aaron Winstanley scored the final goal for Manchester a minute from the end.
Solihull underlined their potential as title challengers, beating champions Cheltenham 7-3. The match was tied at 3-3 after three periods, then Solihull raced clear with goals by Ryan Padbury, Jordan Elliot, Jake Vincent and Matt Madden.
In men's Championship 1, a Chris Armstrong hat-trick in the third period helped Sheffield defeat Team Northumbria 13-9. Sheffield had drawn two previous games - four in all so far this season. Caledonia scored five without reply in the opening period on course to an 11-7 victory over City of Bristol.
Picture (Trevor Hyde): Chris Icely in action for Polytechnic.