<A system of satellites at L-1, L-2, L-4 and L-5 would cover the Moon nicely and could be both comms and I think GPS...or would that be MPS?

Sun-Earth or Earth-Moon Lagrange points, you mentioned both...

You know, placing a satellite in a Lagrange point takes alot of deltaV and for the unstable points (L1-3) you have to keep maintaining the orbit.

Wouldn't it be easier to put 3-4 'repeaters' in a high enough lunar orbit so that reasonable surface coverage could be achieved?

Diagram of the Lagrange Point gravitational forces associated with the Sun-Earth system. WMAP orbits around L2, which is about 1.5 million km from the Earth. Lagrange Points are positions in space where the gravitational forces of a two body system like the Sun and the Earth produce enhanced regions of attraction and repulsion. The forces at L2 tend to keep WMAP aligned on the Sun-Earth axis, but requires course correction to keep the spacecraft from moving toward or away from the Earth.

Note: Image is not to scale