Ragged infill on base layer

Hi all

I am having some fun and games getting my base layer to stick properly. It seems to deposit well on the first pass of the extruder only to rip up on subsequent passes giving a ragged appearance like this:

My current setup is the original bed. I have lightly sanded it to roughen it and clean it with methanol before each print trial.

I can generally get away with this on very small prints, but the moment I try anything bigger this happens.

Any advice much appreciated!

looking at this, maybe your filament has too much humidity ?
reprap.org/wiki/Print_Troublesho … _Excessive