Hi Simon, what a super idea (I think it was Susie who also decided on a spider's web for this theme) - and I think it works well. Good effort on the captures as well.
I'm a complete newbie to macro so I'm not best-placed to advise, but I'd suggest looking at your lighting set up (or, if it was taken in natural light, thinking about repeating on a cloudier day)... for me, all three images would benefit hugely from more diffuse lighting. Getting enough lighting on the subject can be difficult, so a lot of this sort of photography is done with ultra soft but very strong (the "Andrex" of the lighting world, if you will!) flash. You have a few blown highlights which suggest quite harsh directional light.
If you enjoy this sort of photography I'd definitely recommend heading over to the macro section of the forum as the guys (and girls) there are hugely helpful and so knowledgeable. I just hope you like Pringles!
(by the, well done on the pictures and perfectly on theme!)