Anet A8 setup issues

Hi,
I'm new to 3D printing and thought I'd buy a kit to learn as much as I can.
I have an Anet A8 and am trying to get my first print working properly on it.

I've levelled the bed so that in each corner then print head grips a piece of paper with a little resistance, but so the paper can move.

When I try printing, I get very uneven output. The walls seem to be almost non-existent, but when it moves to fill the middle it gets intermittently thicker.
I've attached a picture of what it's currently doing - you can see that the skirt and wall is very thin whilst the middle undulates.
Attachment 12906

So far, I've tried upping the temperature from 200 to 205 and adding a skirt to prime the extruder.
I get very good adhesion to the bed, and the bed feels like it's smooth and flat

I'm printing in 1.75mm PLA with a 0.4mm extruder head

Does anyone have any suggestions as to what might cause this or what I can do about it?