Don't see the need to change to 4-3-3 at all. It's clear that 4-2-3-1 is a solid formation, and successful in Champions League. Look no further than the two German teams.
Dortmund:
Lewandowski
Reus Götze Kuba
Gundogan Bender
Schmelzer Hummels Subotic Piszcszek
Bayern:
Gomez
Ribery Müller/Kroos Robben
Scheinsteiger Martinez
Alaba Dante Boateng Lahm
The biggest difference is that they have pace on the wings, whereas we do not.
Dortmund:
Lewandowski
Reus Götze Kuba
Gundogan Bender
Schmelzer Hummels Subotic Piszcszek
Bayern:
Gomez
Ribery Müller/Kroos Robben
Scheinsteiger Martinez
Alaba Dante Boateng Lahm
The biggest difference is that they have pace on the wings, whereas we do not.